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A M Poisner

Publications and source records attributed to A M Poisner.

16 recordsLinked to original sources
PubMed1992

Prolonged stimulation of bovine adrenal chromaffin cells with arachidonic acid and prostaglandin E2 increases expression of the proenkephalin gene and the secretion of [Met5]-enkephalin.

The effects of long-term exposure of bovine adrenal medullary chromaffin (BAMC) cells to arachidonic acid (AA) and prostaglandin E2 (PGE2) on [Met5]-enkephalin (ME) secretion and expression of the proenkephalin A (proENK) gene were studied. Treatment with various concentrations of AA or PGE2 for 24 hr increased the secretion of ME in a concentration- and time-dependent manner. At high concentrations (10-100 microM), but not low (1-3 microM), AA significantly increased ME secretion by 1 hr. In contrast, the onset time for increase of ME secretion by PGE2 was 3 hr after exposure. The magnitude of increase in ME secretion in the presence of AA or PGE2 continued to increase with time. However, intracellular ME levels in AA- or PGE2-treated cells were not significantly different from that of controls, indicating that elevated levels of ME secretion into the media may be a result of increased biosynthesis of ME. In addition, AA or PGE2 increased proENK mRNA level in a concentration- and time-dependent manner. The onset time for the increase in proENK mRNA in response to PGE2 was 6 hr after exposure. The treatment of BAMC cells with 20 microM cycloheximide (a protein synthesis inhibitor) inhibited both the increased secretion of ME and proENK mRNA level induced by AA and PGE2 in a time-dependent manner, indicating that the delayed secretion of ME and the increase in proENK mRNA level induced by AA and PGE2 require protein synthesis. Indomethacin (a cyclooxygenase inhibitor, 10 microM) effectively inhibited AA-induced responses, whereas 10 microM nordihydroguaiaretic acid (a lipoxygenase inhibitor) was inactive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1990

Short and long term regulation of catecholamine biosynthetic enzymes by angiotensin in cultured adrenal medullary cells. Molecular mechanisms and nature of second messenger systems.

The purpose of this study was to examine the effects of angiotensin on the enzyme activities and gene expression of two catecholamine synthesizing enzymes, tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT), in bovine adrenal medullary (AM) cells. Short term (15 min) incubation of cultured AM cells with 2 nM [Sar1]angiotensin II (s1-AII) did not increase basal secretion of catecholamines; however, longer incubations (3, 24, or 72 h) produced 4-10-fold increases. To determine whether angiotensin affects synthesis of catecholamines, the activities of TH and PNMT were examined. Incubation with s1-AII (15-30 min) decreased the Km of TH for its biopterine cofactor [6R)-5,6,7,8-tetrahydro-1-biopterin dihydrochloride (BH4] without affecting the Vmax, suggesting activation of TH. After long term incubation (72 h) the Km value was identical to that of control, while increases in the apparent Vmax were observed. PNMT activity was unaffected during a 30-min treatment with s1-AII; however, 2-fold increases occurred after a 48-72-h incubation. s1-AII (24 h) increased the relative abundance of TH and PNMT mRNAs, suggesting that the long term increase in enzyme activities reflected increased expression of TH and PNMT genes. Maximal increases were observed at 2 nM s1-AII and the changes were antagonized by saralasin. Induction of TH mRNA by s1-AII was additive to the effects of veratridine or forskolin indicating that effects of angiotensin were not due to membrane depolarization or increased cyclic AMP levels. Incubation with Ca2+ ionophore A23187 increased TH and PNMT mRNA levels in AM cells raising the possibility that the increase in cellular [Ca2+] could mediate effects of angiotensin. Angiotensin-induced increases in TH and PNMT mRNA were inhibited by nifedipine indicating involvement of voltage-dependent Ca2+ channels. In addition, the increases in TH, but not PNMT mRNA, were antagonized by dantrolene, which inhibits mobilization of Ca2+ from intracellular stores. Calmodulin involvement was suggested by the inhibition of s1-AII induced changes in mRNA with 1 microM calmidazolium.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Medulla↗
PubMed1990

Relaxin stimulates the synthesis and release of prorenin from human decidual cells: evidence for autocrine/paracrine regulation.

Porcine relaxin caused a time- and concentration-dependent increase in the release of renin from decidual cells cultured over a 96 h period. The increase in renin release occurred 24-48 h after exposure and was maximal at 48-72 h. Half-maximal stimulation occurred at a relaxin concentration of 5 ng/ml, and maximal stimulation (250-270%) occurred at concentrations greater than or equal to 10 ng/ml. At each time, greater than 95% of the renin released into the medium was in the form of prorenin. The stimulation of renin release was paralleled by a stimulation of cellular renin content and was completely inhibited by cycloheximide, indicating that relaxin also stimulated renin synthesis. Since renin is present in both cytotrophoblast and decidual cells, these results suggest a paracrine and/or autocrine relationship between relaxin- and prorenin-secreting cells.

Cells, Cultured↗
PubMed1990

Stimulation of adrenal medullary cells in vivo and in vitro induces expression of c-fos proto-oncogene.

The nuclear proto-oncogene, c-fos, has been implicated in the coordinated regulation of gene expression during cell proliferation and differentiation. In this study, we have demonstrated the induction of the c-fos gene products in differentiated cells of the adrenal medulla by non-mitogenic signals. Activation of adrenal medullary cells in vivo by insulin-induced hypoglycemia, and in vitro by nicotine or angiotensin resulted in the rapid and transient elevation of c-fos mRNA levels. Induction of the c-fos mRNA by angiotensin and nicotine were accompanied by the appearance of the c-fos protein. The increase in c-fos protein occurred initially in the cytoplasm and, later, in the nucleus, and it was co-localized with tyrosine hydroxylase. Nuclear expression of the c-fos protein was also induced by veratridine, forskolin and the calcium ionophore A231287. The role of calcium in the regulation of the c-fos gene by angiotensin with nifedipine and inhibition of the effects of angiotensin with nifedipine and sphingosine, a protein kinase C inhibitor. Activation of the c-fos gene may play a role in the coordinated induction of genes involved in the long-term adaptation of adrenal medullary cells to increased functional demands.

Adrenal Medulla↗
PubMed1985

Evidence for a role for adenosine 3',5'-monophosphate in progesterone secretion by human chorion.

Experiments were performed to determine whether cells from human chorion can synthesize and release progesterone. Cells were isolated from term chorion laeve by collagenase-DNAse digestion and incubated in RPMI-1640 medium. Freshly isolated cells contained 9.9 +/- 1.1 ng progesterone/10(6) cells, and released 72.0 +/- 7.1 ng/10(6) cells X 24 h in the absence of precursors. When 25-hydroxycholesterol (25HC) served as a precursor, progesterone release into the medium was concentration and time dependent from 1-20 micrograms/ml up to 8 h. When pregnenolone served as a precursor, progesterone secretion followed Michaelis-Menten kinetics (Km = 6.7 microM; maximum velocity, 1.02 nmol/10(6) cells X h). In the presence of 25HC (20 micrograms/ml), progesterone release increased significantly on exposure to cholera toxin (1 microgram/ml), methylisobutylxanthine (0.1 mM), forskolin (0.1 mM), or (Bu)2cAMP (1 mM). Cells maintained in culture released progesterone when fetal calf serum (10%) or 25HC served as precursors. These studies show that trophoblasts from fetal membranes can synthesize and release progesterone from endogenous and exogenous precurors and support the suggestion that cAMP is an important mediator in this process.

1-Methyl-3-isobutylxanthine↗
PubMed1979

The role of cytoskeleton in adreno-medullary secretion.

Chromaffin cells of the adrenal medulla contain prominent arrays of microtubules and microfilaments. One population of microtubules radiates from the cytocentrum and permeates the areas of the cytoplasm containing chromaffin granules; the other population of microtubules forms a subplasmalemmal network together with actin-like microfilaments. Hence, the cytoskeletal elements in chromaffin cells are strategically located to participate in the mobility of chromaffin granules to the cell surface and to regulate access of the granules to the plasma membrane during exocytosis. Agents which effect the integrity of the cytoskeleton clearly affect the secretory process in a manner which indicates that the microtubules and microfilaments play an active role in the release process.

Adrenal Medulla↗
PubMed1976

Properties of renin granules isolated from rat kidney.

Renin granules from rat kidney prepared at 25 degrees C show greater stability at 25 degrees C than at 0 degrees C when incubated in ionic medium. The sum of the renin in the supernatant fluid plus that in the pellet was the same at 25 degrees C as at 0 degrees C, thus ruling out the possibility that the extra release at 0 degrees C merely represented greater stability of free renin at 0 degrees C. In common with other secretory granules, renin granules were most stable at pH 6.0 and were osmotically sensitive. In contrast to neurosecretory and chromaffin granules, renin granules were stabilized by Mg-ATP in ionic medium. This result is similar to studies by others on lysosomes. It is concluded that the renin granules membrane shares many of the properties of other granule membranes. Some of these properties (temperature and pH lability) will have to be considered in the design of future experiments on renin storage and release.

Adenosine Triphosphate↗
PubMed1976

Direct stimulation of renin release by calcium.

Calcium directly stimulates renin release from rat kidney slices previously treated with calcium-free medium. The stimulant effect of calcium (0.5 or 6.0 mM) is not seen without the period of calcium depletion. The stimulant effect of calcium is still present in sodium-free medium but is reduced when the incubation is performed at 20 degrees instead of 37 degrees. The results suggest that the underlying mechanism of renin release may be comparable to that of catecholamine release, involving calcium-dependent and energy-dependent steps.

Animals↗
PubMedDate not supplied

Cyclic AMP as a second messenger for prorenin release from human decidual cells.

The possible roles of cyclic AMP and protein kinase C in the release of renin from human decidual cells were investigated by examining renin release from monolayers of decidual cells exposed for 72 h to agents that increase intracellular cAMP or activate protein kinase C. Dibutyryl cAMP (10-1000 microM caused a dose-dependent stimulation of renin release after a 24-h exposure. Maximal stimulation, 410 per cent greater than that of control cells, occurred at 72 h, and 98 per cent of the renin released into the medium was in the form of prorenin. Forskolin (10-1000 microM) and cholera toxin (CT. 20-1000 ng/ml), both of which stimulate adenyl cyclase, also stimulated prorenin release. Phorbol myristate acetate (PMA), an activator of protein kinase C, had little effect on basal prorenin release at 100 nM but potentiated the stimulation of prorenin release by cAMP and CT. The effects on prorenin release were paralleled by stimulation of active renin release. The results of this study therefore implicate cAMP and protein kinase C in the regulation of prorenin release from decidual cells and suggest that prorenin release from the decidua and other tissues is regulated by the same second messengers.

Analysis of Variance↗