Biomedical subjects

Catarina S Porto

Publications and source records attributed to Catarina S Porto.

3 recordsLinked to original sources

PubMed2003

Upregulation of muscarinic receptors by long-term nitric oxide inhibition in the rat ileum.

1. The aim of the present study was to examine the effects of long-term nitric oxide (NO) blockade on contractions of the rat ileum induced by muscarinic agonists. 2. Male Wistar rats received the NO synthesis inhibitor NG-nitro-l-arginine methyl ester (l-NAME; 20 mg/rat per day) in drinking water for 7, 15, 30 and 60 days. Concentration-responses curves to methacholine and carbachol were obtained and pEC50 values were calculated. Saturation binding assays were performed in membranes prepared from rat ileum after 60 days of l-NAME treatment and the dissociation constant (KD) and maximal number of binding sites (Bmax) were determined by Scatchard analysis. 3. The NO synthase activity of the ileum was markedly reduced in all l-NAME-treated groups. At 60 days after l-NAME treatment, a significant increase in the potency of methacholine (fourfold) and carbachol (threefold) was observed. In binding studies, we found a significant increase in Bmax for [3H]-quinuclidinyl benzilate of approximately 57% in the l-NAME treated group without any significant change in KD values. The contractile response to methacholine was not modified by the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (3 micro mol/L). No morphological alterations in the rat ileum were observed in l-NAME-treated rats. 4. Our findings suggest that treatment with l-NAME for 60 days induces a marked increase in the potency of methacholine and carbachol, as well as an increase in receptor number in the rat ileum.

Animals↗

PubMed2002

Alpha1-adrenoceptor subtypes in rat epididymis and the effects of sexual maturation.

We have characterized the expression of alpha1-adrenoceptor in epididymis from rats in different stages of sexual maturation: 40 (immature), 60 (young adult), and 120 (adult) days of age. Plasma testosterone levels were low in the immature animals but increased significantly in the 60- and 120-day-old animals. These changes were followed by a progressive increase in rat body weight and in caput and cauda epididymis relative weight. Reverse transcription polymerase chain reaction assay indicated that alpha1a-, alpha1b-, and alpha1d-adrenoceptor transcripts were present in both caput and cauda epididymis from adult rats. Ribonuclease protection assays further indicated that the expression of these alpha1-adrenoceptor transcripts differed with age and epididymal region analyzed. Prazosin (nonselective alpha1 antagonist), 5-methyl urapidil (alpha1A-selective), and BMY 7378 (alpha1D-selective) displaced [3H]prazosin binding curves in caput and cauda epididymis from 40- and 120-day-old rats. The potency order for these antagonists, as calculated from the negative logarithm of the inhibition constant (pK(i)) values for the high-affinity sites, indicated a predominant population of alpha1A-adrenoceptor subtype in caput and cauda epididymis from adult animals. Differences in pK(i) values in caput and cauda epididymis from immature and adult animals also suggested that the relative amount of alpha1-adrenoceptors, at the protein level, is modulated by sexual maturation. Taken together, the changes in alpha1-adrenoceptor expression during sexual maturation may suggest specific roles for these receptors in epididymal function.

Adrenergic alpha-Antagonists↗

PubMedDate not supplied

Segment-specific decrease of both catecholamine concentration and acetylcholinesterase activity are accompanied by nerve refinement in the rat cauda epididymis during sexual maturation.

In the present work, histochemical and biochemical studies were conducted to analyze changes in the pattern of autonomic innervation during sexual maturation, using the rat epididymis as a model. Glyoxylic acid histochemistry and immunohistochemical studies against dopamine beta-hydroxylase (DbetaH) and acetylcholinesterase (AChE) indicated a reduction in the amount of catecholaminergic and AChE-positive neurons, fibers, and puncta detected in the cauda epididymis of adult rats (120 days old), when compared to immature (40 days) and young adult (60 days) animals. No obvious age-related variations were detected in the few catecholaminergic and AChE-positive fibers and puncta present in the caput region. AChE-positive fibers were found sorting out among epithelial cells and ending free upon the epithelial surface or into the tubular lumen of the cauda region of adult rats. Furthermore, a positive staining for AChE in epithelial cells was also detected in the caput and cauda epididymis in all ages studied. Biochemical analysis confirmed a significant decrease in noradrenaline concentration as well as AChE activity in the cauda epididymis with sexual maturation. Immunohistochemical studies against microtubule-associated protein 1B (MAP 1B), a neuronal cytoskeletal marker, further substantiated the quantitative changes observed in catecholaminergic and AChE-positive neuronal elements in the cauda epididymis. Thus, our results documented segment-specific variations in noradrenaline concentration and AChE activity during epididymal sexual maturation and suggest that such variations result, at least in part, from the refinement of the autonomic innervation pattern with age.

Acetylcholinesterase↗