Effect of estrogen treatment of calcium uptake by the rat uterine smooth muscle

doi:10.1016/0024-3205(83)90076-0

Life Sciences

Volume 32, Issue 4, 24 January 1983, Pages 315-319

https://doi.org/10.1016/0024-3205(83)90076-0 Get rights and content

Abstract

The effect of estrogenization on cellular ⁴⁵Ca uptake by the isolated uterine strips was studied. Whereas estrogenization 1 h before sacrifice of ovariectomized rats caused no significant change in Ca uptake by the isolated uteri, exposure to estrogen 24 h before sacrifice resulted in a significant increase in uptake. Following continuous exposure for 72 h to estrogen, the uptake of Ca was increased by more than two-fold. Increased Ca uptake following estrogenization may largely account for the increased contractile responses of the uterine smooth muscle particularly those induced by potassium depolarization.

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The aim of this study was to investigate the rapid response pathway and gene and protein expression profiles of the rat testis in response to estradiol (E₂) and 1α,25(OH)₂ vitamin D₃ (1,25-D₃), to understand how they mediate their effects on the first spermatogenic wave. To do this, we compared the effects of 1,25-D₃ and E₂ on ⁴⁵calcium(Ca²⁺) uptake and the involvement of estrogen receptors (ESR) in their rapid responses. Additionally, we studied the downstream signal transduction effects of 1,25-D₃ and E₂ on cyclin A1/B1 and cellular cycle protein expression. As previously observed for 1,25-D₃, E₂ also increased ⁴⁵Ca²⁺ uptake in immature rat testes via voltage-dependent Ca²⁺ channels, Ca²⁺-dependent chloride channels and via the activation of protein kinase C, protein kinase A and mitogen-activated protein kinase kinase (MEK). Elevated aromatase expression by testes was observed in the presence of 1,25-D₃ and both hormones decreased ESR mRNA expression. Furthermore, 1,25-D₃ and E₂ diminished cyclin A1 mRNA expression, but E₂ did not affect cyclin B1 mRNA levels. Consistent with these findings, the immunocontent of cyclin A1 and B1 in the testes was also increased by 1,25-D₃ and E₂. 1,25-D₃ increased expressions of the p16 and p53 proteins, supporting the anti-proliferative and pro-apoptotic properties of 1,25-D_3, while E₂ also augmented p16. Data indicate that both hormones trigger rapid responses at the plasma membrane that may control the expression of gene and proteins related to cell cycle regulation, and thereby modulate spermatogenesis.
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New ionic targets of 3,3′,5′-triiodothyronine at the plasma membrane of rat Sertoli cells
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Betulinic acid (BA) has been described as an insulin secretagogue which may explain its potent antihyperglycemic effect; however, the exact role of BA as an insulinogenic agent is not clear. The aim of this study was to investigate the mechanism of BA on calcium influx and static insulin secretion in pancreatic islets isolated from euglycemic rats. We found that BA triggers calcium influx by a mechanism dependent on ATP-dependent potassium channels and L-type voltage-dependent calcium channels. Additionally, the voltage-dependent and calcium-dependent chloride channels are also involved in the mechanism of BA, probably due to an indirect stimulation of calcium entry and increased intracellular calcium. Additionally, the downstream activation of PKC, which is necessary for the effect of BA on calcium influx, is involved in the full stimulatory response of the triterpene. BA stimulated the static secretion of insulin in pancreatic islets, indicating that the abrupt calcium influx may be a key step in its secretagogue effect. As such, BA stimulates insulin secretion through the activation of electrophysiological mechanisms, such as the closure of potassium channels and opening of calcium and chloride channels, inducing cellular depolarization associated with metabolic-biochemical effects, in turn activating PKC and ensuring the secretion of insulin.
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Effect of estrogen treatment of calcium uptake by the rat uterine smooth muscle

Abstract

Trends Pharmacol. Sci.

Biochem. Pharmacol.

J. Pharm. Sci.

Steroids

Female sex steroids

J. Physiol. (London)