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Biomedical subjects

G J Christ

Publications and source records attributed to G J Christ.

At least 73 records · Page 4Linked to original sources
PubMed1995

Endothelin-1 as a putative modulator of erectile dysfunction: I. Characteristics of contraction of isolated corporal tissue strips.

Normal erectile physiology is heavily dependent on a delicate balance between the effects of endogenous vasoconstricting and vasorelaxing hormones on the tone of the corporal smooth muscle. Recent studies indicate that endothelin-1 (ET-1) is present and physiologically active in the human corpora. The primary goal of the present investigation was to further define the role of ET-1 in corporal physiology and to ascertain whether it might play a role in augmenting corporal tone in vivo, as reported in other vascular tissues. Thus, we conducted pharmacological studies of ET-1-induced steady-state contractions in isolated human corporal smooth muscle strips to determine if there were any detectable age- or diabetes-related alterations in ET-1-induced contractions. For statistical analysis, the patient population was divided into 2 age groups, A (< or = 59 years of age; = 11 patients) and B (> or = 60 years of age; n = 7 patients), and further subdivided into 2 diagnostic categories, diabetic (n = 7 patients) and nondiabetic (n = 11 patients). Construction of cumulative concentration response curves (CRCs) for ET-1-induced contractions revealed characteristically slow onset and long-lasting responses. Endothelin-1 CRC data were computer fit to the logistic equation to derive Emax (calculated maximal response), pEC50 (negative logarithm of the concentration that elicits one-half of the calculated maximal response) and slope factor (n) values. Two-factor analysis of variance revealed no detectable age- or diabetes-related alterations, nor any age-diabetes interaction in any of the logistic parameters. Furthermore, logistic analysis of ET-1 CRC data on 14 isolated corporal tissue strips derived from 3 potent patients with documented spontaneous erections revealed no differences in ET-1 contractility from that observed for patients with organic erectile dysfunction. Importantly, despite an apparent absence of age- or diabetes-related alterations in ET-1-induced steady-state contractions, preliminary studies demonstrated that coadministration of the alpha 1-adrenergic agonist phenylephrine and ET-1 produce much greater contractile responses than those observed in the presence of phenylephrine (PE) alone. Moreover, the magnitude of the augmentation was precisely that predicted by a model for simple additivity of agonist effects. Such observations suggest that the physiological relevance of ET-1 to corporal physiology may be related to its ability to augment the contractile responses of other vasomodulators present in the human corpora, in particular, perhaps modulating the contractile responses to sympathetic activity.

Diabetes Mellitus↗
PubMed1995

An analysis of the Maxi-K+ (KCa) channel in cultured human corporal smooth muscle cells.

Previous studies have demonstrated that cultured corporal smooth muscle cells have prominent outward K currents composed of several different K channel subtypes. The goals of the present investigation were (1) to assert the nature of these channels and to evaluate the characteristics of the most predominant of these channel subtypes, the Maxi-K+ (KCa) channel, and (2) to compare KCa channel behavior in cultured corporal smooth muscle cells derived from the human corpus cavernosum of two distinct patient populations. The patient population was subdivided into two broad diagnostic categories: Group 1: 4 patients without evidence of organic disease of the corpus cavernosum, 3 of whom had documented erections; and Group 2: 4 patients with organic erectile dysfunction. Consistent with previous observations, 3 different K channel subtypes were detected in both patient populations, with corresponding conductances of 180, 100 and 40 pS, respectively. The approximately 183 pS channel was identified as the KCa channel based on its selective permeability to K+ and the fact that its open probability was modulated by both membrane potential and intracellular calcium levels. Specifically, the relative permeability of the 183 pS KCa channel to K+, Rb+, and NH4+ was 1.00:0.64:0.46. The channel was virtually impermeable to Na+ and Li+ (relative permeability < 0.02). In addition, the KCa channel was responsible for more than 90% of the outward K+ current passed through the cell membrane when depolarized. Furthermore, pharmacological studies using the K channel blocker tetraethylammonium ion (TEA) revealed that the sensitivity of KCa channels to TEA inhibition (as judged by the [TEA] required to block one-half of the outward whole cell current induced by a 90 mV depolarizing pulse) in cells from Group 1 patients was 1.05 +/- 0.22 mM. (n = 10 cells), while in sharp contrast the observed value for cells from Group 2 patients was 12.7 +/- 3.8 (n = 9 cells). The difference between the two groups was highly significant. These observations confirm and extend our previous studies to suggest that the KCa channel plays an important role in corporal smooth muscle physiology and, moreover, that alterations in the function/regulation of KCa channels may be an important feature of organic erectile dysfunction. As such, altered KCa channel behavior may contribute to an impaired hyperpolarizing ability of corporal smooth muscle, possibly altering intracellular calcium homeostasis and, perhaps, corporal smooth muscle reactivity and tone.

Calcium↗
PubMed1994

Augmentation in the kinetic characteristics of phenylephrine- and 5-hydroxytryptamine-induced contractions in the isolated rat aorta following eight weeks of STZ-diabetes.

Kinetic studies were conducted on the contractile response elicited by phenylephrine (PE) and 5-hydroxytryptamine (5-HT) activation of the alpha 1-adrenergic- and 5-HT2 receptor subtypes, respectively, in aortic rings isolated from streptozotocin (STZ)-diabetic and age-matched control rats. The maximal PE- and 5-HT-induced contractile responses were separated into distinct phasic and tonic components, and the tonic portion of the response was assessed by evaluation of the calculated maximal rate constant for onset of contraction (kobsmax; min-1). Statistical analysis revealed that the mean kobsmax values for PE alone (10 microM), 5-HT alone (10 microM) and mixtures of PE and 5-HT (10 microM each) were significantly greater in diabetic animals than in age-matched control animals. These increases in kobsmax resulted in significant diabetes-related increases in the rate and relative magnitude of response generation during the initial minutes of contraction. Such observations emphasize the importance of kinetic studies, and given the central role played by the aorta in cardiovascular homeostasis, suggest that altered aortic contractility may play a role in some aspects of diabetic vascular disease. Moreover, if these kinetic alterations reflect a more generalized feature of diabetic vasculature (e.g., resistance vessels), then it is conceivable that such changes may further exacerbate diabetic vasculopathy.

Animals↗
PubMed1994

Cholinergic modulation of immunoglobulin secretion from avian plasma cells: the role of calcium.

The existence of a functional connection between the nervous and immune systems has long been argued. To determine if such a link exists in the secretory immune system, we have examined the avian lacrimal gland (Harderian gland) which contains large numbers of plasma cells. We have shown that these plasma cells bind an antibody to muscarinic acetylcholine receptor and that carbachol, an acetylcholine agonist, increases the secretion rate of IgG by these cells above a constitutive baseline level. This neurotransmitter-dependent increase of immunoglobulin secretion requires an influx of Ca2+, whereas the constitutive baseline secretion is apparently less dependent on such a flux. Furthermore, the Ca2+ flux appears to be mediated by voltage-dependent calcium channels. These data support the hypothesis that plasma cells can respond to neurotransmitters and, in the case of acetylcholine, increase immunoglobulin secretion.

Animals↗
PubMed1994

Dynamic gap junctional communication: a delimiting model for tissue responses.

Gap junctions are aqueous intercellular channels formed by a diverse class of membrane-spanning proteins, known as connexins. These aqueous pores provide partial cytoplasmic continuity between cells in most tissues, and are freely permeable to a host of physiologically relevant second messenger molecules/ionic species (e.g., Ca2+, IP3, cAMP, cGMP). Despite the fact that these second messenger molecules/ionic species have been shown to alter junctional patency, there is no clear basis for understanding how dynamic and transient changes in the intracellular concentration of second messenger molecules might modulate the extent of intercellular communication among coupled cells. Thus, we have modified the tissue monolayer model of Ramanan and Brink (1990) to account for both the up-regulatory and down-regulatory effects on junctions by second messenger molecules that diffuse through gap junctions. We have chosen the vascular wall as our morphological correlate because of its anisotropy and large investment of gap junctions. The model allows us to illustrate the putative behavior of gap junctions under a variety of physiologically relevant conditions. The modeling studies demonstrated that transient alterations in intracellular second messenger concentrations are capable of producing 50-125% changes in the number of cells recruited into a functional syncytial unit, after activation of a single cell. Moreover, the model conditions required to demonstrate such physiologically relevant changes in intercellular diffusion among coupled cells are commonly observed in intact tissues and cultured cells.

Animals↗
PubMed1994

Characterization of cyclic AMP accumulation in cultured human corpus cavernosum smooth muscle cells.

Intracavernous pharmacotherapy relies heavily on the use of vasoactive agents which act by increasing intracellular cAMP levels in human corpus cavernosum smooth muscle. Yet little is known about the cAMP generating system in this tissue, and how it may affect observed patient variability. Thus, the goal of these studies was to better characterize the biochemistry of cAMP formation in human corpus cavernosum smooth muscle, and thus provide more insight into the mechanisms of corporal smooth muscle relaxation in vivo. We studied both receptor and nonreceptor mediated increases in cAMP formation in short-term cultures of human corpus cavernosum smooth muscle cells. Both isoproterenol (ISO) and prostaglandin E1 (PGE1) produced concentration-dependent increases in cAMP, but histamine, serotonin and vasoactive intestinal polypeptide did not. Forskolin, a relatively specific activator of adenylate cyclase, was also a potent stimulant of cAMP formation in these cells. Moreover, there was a direct correlation between the degree of forskolin-induced cAMP accumulation in cultured corporal smooth muscle cells and the magnitude of the forskolin-induced relaxation response of precontracted isolated corporal smooth muscle strips. Prostaglandin E1 and ISO concentration response curves (CRCs) were then assayed in the absence and presence of subthreshold forskolin (0.1 microM.). In the presence of forskolin, the calculated maximal PGE1-induced cAMP accumulation (Emax) was significantly greater than that elicited by PGE1 alone, ISO alone, or ISO + forskolin (p < or = 0.02). In addition, a fixed molar ratio (FMR) (PGE1:ISO) protocol was used to demonstrate that both 80:20 and 70:30 FMRs (but not 95:5 or 90:10), were associated with significantly greater cAMP Emax values than that observed for PGE1 alone (p < or = 0.01). These data provide direct evidence that the degree of cAMP formation in cultured corporal smooth muscle cells is strongly correlated with the magnitude of relaxation of isolated corporal smooth muscle strips. In addition, since simultaneous activation of distinct components of the cAMP generating system produces significant increases in maximal intracellular cAMP accumulation, this suggests that such drug combinations may also augment corporal smooth muscle relaxation in vitro and in vivo.

Alprostadil↗
PubMed1993

Relationship between contraction and relaxation in human and rabbit corpus cavernosum.

Although alterations in corporeal smooth muscle tone undoubtedly play an important role in the etiology of erectile dysfunction, the relationship between the degree of corporeal smooth muscle contraction and the magnitude of the observed relaxation response has never been quantitated. Thus, in vitro studies were conducted to examine the relationship between alpha 1-adrenergic contractility, and relaxations elicited by the clinically and physiologically relevant vasorelaxants, nitroglycerin, nitroprusside, and prostaglandin E1. Corporeal tissues strips were isolated from impotent and potent men, as well as sexually mature rabbits, and precontracted over a wide range of phenylephrine doses, prior to exposure of each tissue to the same dose of vasorelaxant. Plots of percent contraction versus percent relaxation revealed that the relationship between contraction and relaxation was accurately described by a first order linear equation, and characterized by an inverse relationship in all tissues studied, for all vasorelaxants examined. Statistical analysis indicated that the slope of the regression line was significantly greater than unity in all corporeal tissues obtained from patients with organic impotence; however, corporeal tissues obtained from patients with documented erections and from sexually mature rabbits had significantly lower slopes that were indistinguishable from unity. The existence of an inverse relationship between contraction and relaxation, even in the absence of organic disease, emphasizes the importance of the level of basal corporeal smooth muscle tone per se. These studies provide further evidence implicating heightened adrenergic tone as a significant etiologic factor in erectile dysfunction.

Alprostadil↗
PubMed1993

Gap junctions formed of connexin43 are found between smooth muscle cells of human corpus cavernosum.

Despite sparse autonomic innervation, the smooth muscle cells of the corpus cavernosum relax and contract synchronously to achieve penile erection and flaccidity. As with other smooth muscle cell types, the excitation process in the corpora is presumably propagated through gap junctions to allow the diffusion of current-carrying ions and second messenger molecules from cell to cell. Using both molecular and immunocytochemical techniques, we have identified gap junctions between human corporal smooth muscle cells in situ and in culture. Northern analyses demonstrated that corporal smooth muscle cells express the gap junction protein connexin43, but not connexin26 mRNA. Immunoblots showed the presence of connexin43 isoforms, whereas connexin32 was not detected. Immunocytochemical studies in cultured cells identified prominent connexin43 immunoreactive puncta between cells, as well as within the cytoplasm. In addition, gap junction membranes both in situ and in culture were labelled in thin section by anti-connexin43 antibodies using the immunogold technique. We conclude that the presence and distribution of gap junctions in this sparsely innervated tissue may provide an important mechanism of intercellular communication among the smooth muscle cells, and thus play a major role in coordinating tissue contraction and relaxation.

Blotting, Northern↗
PubMed1993

The role of gap junctions and ion channels in the modulation of electrical and chemical signals in human corpus cavernosum smooth muscle.

Intercellular communication through aqueous intercellular channels, known as gap junctions, has been postulated to provide an important mechanism for coordinating the rapid and synchronous responses of corporal smooth muscle during human penile erection and detumescence. Mathematical modeling analyses of drug diffusion were utilized to examine the potential physiological importance of the intercellular pathway to the regulation of smooth muscle tone in the human corpus cavernosum. In addition, patch clamp analyses and optical imaging studies were conducted to assess the ionic basis for cellular excitability and homeostasis in cultured corporal smooth muscle cells. In short, the computer modeling studies demonstrated that intercellular communication through gap junctions is likely to be the 'preferred' pathway for coordination of cellular activation and syncytial smooth muscle responses in this tissue. Moreover, the observed ion channel diversity reveals even further complexities to the modulation of corporal smooth muscle tone.

Calcium Channels↗
PubMed1993

Gap junctions modulate tissue contractility and alpha 1 adrenergic agonist efficacy in isolated rat aorta.

Immunocytochemical analysis, using antibodies directed against connexin43, revealed abundant gap junctions between smooth muscle cells in intact aorta from Fischer 344 rats. Therefore, the authors evaluated the potential contribution of these intercellular junctions to contractile responses elicited by alpha 1 adrenergic receptor activation in rat aortic rings. Preincubation with the selective junctional uncoupling agent heptanol (200 microM) diminished the magnitude of contractions induced by the low-efficacy partial agonist oxymetazoline (1-3 microM) by 50.6 +/- 4.5% (P < .01; n = 16 rings from 16 rats) but had no effect on equivalent contractions induced by the high-efficacy agonist phenylephrine (0.1 microM; n = 16 rings from 16 animals). Reduced phenylephrine contractility was observed at higher heptanol concentrations (500 microM). However, neither 200 nor 500 microM heptanol altered the magnitude of contractions elicited by 60 mM KCl, indicating that tissue contractility per se was unaffected by heptanol. In calcium-free solution, the magnitude of the phasic contraction induced by phenylephrine was three-fold greater than the magnitude of the oxymetazoline-induced phasic contraction (P < .001) but the phasic responses to both agonists were unaffected by the same heptanol concentrations that significantly diminished their steady-state responses. Because heptanol, at the concentrations used, has selective pharmacological actions on gap junctions, these studies provide additional support for a role of gap junctions in the maintenance and modulation of vasomotor tone. In rat aorta, junctional transfer of alpha 1 adrenergic-receptor activated second-messenger molecules appears to be an important modulator of tissue contractility and agonist efficacy.

Adrenergic alpha-Agonists↗
PubMed1992

Gap junction-mediated intercellular diffusion of Ca2+ in cultured human corporal smooth muscle cells.

Ratio imaging using the calcium-sensitive probe fura-2 was employed to study intracellular calcium concentrations and intercellular calcium flux through gap junctions in homogeneous vascular smooth muscle cell cultures derived from the human corpora cavernosa. Microinjection techniques demonstrated that fura-2 free acid was freely diffusible through gap junctions between cultured cells. The resting intracellular calcium level in fura-2-loaded cells was 176.9 +/- 10.5. A robust increase in intracellular calcium was seen in response to both phenylephrine and the calcium ionophore A23187. Microinjection of Ca2+ into individual smooth muscle cells always resulted in significant, although temporally delayed, increases in intracellular calcium levels in adjacent cells; this intercellular calcium flux was reversibly blocked by inhibition of gap junctional communication with 2 mM heptanol. However, although microinjection of D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] into individual smooth muscle cells always produced significant increases in intracellular calcium levels in the injected cell, the intercellular spread of Ca2+ in response to Ins(1,4,5)P3 was more variable than for Ca2+ injections. These studies demonstrate that Ca2+, and perhaps Ins(1,4,5)P3 as well, can diffuse between smooth muscle cells through gap junction channels.

Alcohols↗
PubMed1992

Kinetic characteristics of alpha 1-adrenergic contractions in human corpus cavernosum smooth muscle.

Kinetic studies were conducted on the contractile response elicited by phenylephrine (PE) activation of the alpha 1-adrenergic receptor subtype in vascular smooth muscle isolated from the corpus cavernosum of impotent men. PE-induced contractions were separated into distinct phasic and tonic components, and the tonic portion was analyzed using a first-order rate equation to determine the maximal rate constant for onset of contraction (kobs max) and the maximum amplitude of the steady-state contractile response (Req max). The kobs max value in tissues from insulin-dependent diabetic patients was significantly greater than that in tissues from either noninsulin-dependent diabetics or nondiabetics. Additionally, the mean kobs max value in older patients (60-70 yr) was significantly greater than the mean kobs max value in younger patients (32-59 yr). Significant diabetes-related, but not age-related, alterations were also found in Req max. The observed changes in contractility resulted in dramatic age- and pathology-dependent alterations in the initial rate and/or magnitude of PE-induced response generation. These kinetic studies extend our previous observations at steady state and provide further evidence for heightened corporal tissue tone in the etiology of erectile dysfunction.

Aging↗
PubMed1991

Intercellular communication through gap junctions: a potential role in pharmacomechanical coupling and syncytial tissue contraction in vascular smooth muscle isolated from the human corpus cavernosum.

Kinetic and steady-state protocols were used to examine the effects of disruption of intercellular communication with heptanol, on contractile responses elicited by activation of the alpha 1-adrenergic receptor in human corporal vascular smooth muscle. For the steady-state studies, strips of corporal tissue from 19 patients were submaximally precontracted with phenylephrine (PE) and then relaxed by the cumulative addition of heptanol. Heptanol completely and reversibly relaxed all tissues studied in a concentration-dependent manner. The heptanol concentration response data were then computer fit to the general logistic equation to obtain pEC50 (negative logarithm of the concentration that elicits one-half of the maximal effect) and slope factor values, with Emax (maximal relaxation) set to 100%. The mean pEC50 and slope factor values, respectively, were 2.86 +/- 0.04 and 1.86 +/- 0.17. Furthermore, kinetic studies on corporal tissues from a subset of the patient population (11 patients) revealed that preincubation of tissues with 2 mM heptanol caused a significant decrease in both the rate and magnitude of PE-induced contractions in all tissues studied, without affecting the rate constant for onset of contraction (k(obs)). The present results on intact tissue extend our previous observations on cultured corporal cells, and support the supposition that intercellular communication through gap junctions may play an important role in the initiation, maintenance and modulation of alpha 1-adrenergic contractions in human vascular smooth muscle.

Adult↗
PubMed1991

Age-dependent alterations in the efficacy of phenylephrine-induced contractions in vascular smooth muscle isolated from the corpus cavernosum of impotent men.

Steady-state contractile responses elicited by phenylephrine activation of the alpha 1-adrenergic receptor subtype were studied in vascular smooth muscle strips isolated from the corpus cavernosum of impotent men. The dissociation constant of phenylephrine was determined by the method of partial irreversible receptor inactivation over a wide range of alpha 1-adrenergic receptor alkylation levels. Statistical analysis of mean population values revealed a significantly greater mean efficacy for phenylephrine-induced contractions in older patients (60-73 years old) than in younger patients (40-59 years old), in the absence of similar alterations in the mean phenylephrine dissociation constant (affinity). In addition, there was no significant effect of the diabetic state on the mean phenylephrine affinity or efficacy estimates. However, despite the absence of age- or pathology-dependent variations in agonist affinity, as assessed by group mean calculations, a detailed examination of all isolated tissues on an individual basis revealed that the phenylephrine affinity estimates varied over a range of almost two orders of magnitude. Furthermore, a linear regression analysis revealed a highly significant positive correlation between agonist affinity and the location of the phenylephrine concentration-response curve, which was characterized by a slope significantly less than unity. In conclusion, an increased efficacy of phenylephrine-induced contractions in vitro is consistent with the hypothesis that augmented corporal vascular smooth muscle contractility in vivo may contribute to the pathophysiology of impotence in older patients.

Adrenergic alpha-Agonists↗
PubMed1991

Mutual-effect amplification of contractile responses elicited by simultaneous activation of alpha-1 adrenergic and 5-hydroxytryptamine2 receptors in isolated rat aorta.

5-Hydroxytryptamine (5-HT), and the selective alpha-1 agonists phenylephrine (PE) and oxymetazoline (OXY), were used to study the effects of simultaneous coactivation of the 5-HT2 and alpha-1 adrenergic receptors, respectively, on the contractile responses of isolated rat aortic rings. Dissociation constants (KA) were determined for each of the agonists at their respective receptor subtypes. The KA values for PE and OXY at the alpha-1 receptor were 316 nM and 1.82 microM, respectively, while the KA for 5-HT at the 5-HT2 receptor was 478 nM. Concentration-response curves for each agonist were analyzed by the Black and Leff operational model of pharmacological agonism to determine efficacy (tau) and slope factor values. The estimated tau for PE (16.02) was much greater than the tau for either OXY (4.15) or 5-HT (2.95), which had similar efficacies. Using a previously described drug concentration paradigm, a mutual-effect amplification of the 5-HT-induced contractile response was observed with mixtures of 5-HT and PE, whereas mixtures of OXY and 5-HT elicited a mutual-effect amplification of the observed response to OXY alone. In both cases, the theoretical concentration-response curve constructed using the Poch and Holzmann method of equiactive substitution demonstrated that mutual-effect amplification was largely the result of simple additivity of agonist effects. In addition, estimates of tau and slope factor determined from the Black and Leff equation were substituted into the Leff model of mutual-effect amplification and used to accurately predict the location of the concentration-response curves elicited by mixtures of 5-HT and PE, as well as mixtures of OXY and 5-HT. This represents the first time a mathematical model has been used to accurately predict the outcome of coactivation of the alpha-1 and 5-HT2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Determination of agonist dissociation constants in isolated vasculature: equivalence of estimates obtained by the method of partial irreversible receptor inactivation and a novel application of the operational model of pharmacological agonism.

Steady-state contractile responses elicited by activation of the proportional 1-adrenergic and 5-HT2 receptors in isolated rat and rabbit aorta, respectively, were analyzed. Agonist dissociation constants (KA's) obtained by the method of partial irreversible receptor inactivation were compared to KA values determined by fits of the operational model of pharmacological agonism to single concentration response curves (CRCs). The observed nature of the KA estimates obtained with the Furchgott method for phenylephrine (PE) and oxymetazoline (OXY) at the proportional 1-adrenergic receptor and for 5-hydroxytryptamine (5-HT) at the 5-HT2 receptor in isolated rat aorta, and for PE and 5-HT at the proportional 1-adrenergic and 5-HT2 receptors, respectively, in isolated rabbit aorta, was consistent with the hypothesis that the density of membrane receptors is greatly in excess of the density of transducer proteins (i.e., [Ro] much greater than [To]) in these systems. Therefore, KA, efficacy and slope factor estimates were also obtained by computer fits of the operational model to single agonist CRCs in both rat and rabbit aorta, with the empirically determined tissue maximal response (Tmax) substituted for the theoretical parameter Em. In all cases, the mean pKA estimates obtained with the operational model closely approximated and were strongly correlated with the mean pKA estimates determined by the Furchgott method. These studies suggest that, at least in some vascular preparations, Tmax is a good estimate of Em, and moreover, that Em may be not only a specific characteristic of a given receptor-effector system as previously demonstrated by Black and Leff, but that Em may also describe a more general feature of tissue responsiveness that is shared among distinct membrane receptors coupled to similar effector systems. In conclusion, when receptor inactivation studies have indicated that the condition [Ro] much greater than [To] exists, Tmax can be substituted into the operational model to provide valid estimates of agonist KA values at distinct receptor subtypes, in the absence of receptor alkylation.

Animals↗