Seasonal variations in the function of the endocrine pancreas in Psammomys obesus.

The aim of this work was to determine whether Psammomys obesus living in its natural habitat displays variation in the function of the endocrine pancreas. Live animals were collected regularly through the year by strip sampling. Plasma glucose varied during the year.

Modulation of Leydig cell testosterone production by secretory products of macrophages.

Unstimulated macrophages from testes inhibited the production of testosterone by Leydig cells from adult, but not immature, Sprague-Dawley rats (significant after 48 h). Similar results were observed with unstimulated macrophage-conditioned media, suggesting that the observed effect was mediated by one or more secretory products. None of these substances was interleukin-1, since macrophage supernatants tested negative in an interleukin-1 alpha and interleukin-1 beta sensitive, thymocyte assay.

D1 receptors modulate striatal dopamine release induced by the stimulation of both D1 and D2 receptors: in vivo voltammetric data revisited.

Here we re-examine previous data that demonstrated lasting effects of the selective D1 receptor agonist SKF 38393, the selective D2 receptor agonist LY 171555, and of mixed SKF 39383 + LY 171555 upon striatal DA release. We demonstrate that the administration of mixed SKF 38393 + LY 171555 and of SKF 38393 administered alone induced similar time-course effects upon striatal DA release that showed significant parallel developments. We discuss these data in the light of the current literature and we suggest that D1 receptors could play a modulating role on the striatal DA activity and the release of DA in the caudate-putamen.

CCK and PYY do not participate in the delayed inhibition of pancreatic secretion, after stimulation by duodenal oleic acid infusion.

The role played by CCK in the stimulation of pancreatic secretion by duodenal infusion of oleic acid in conscious rats was studied using a potent and specific CCK receptor antagonist. CR-1409 did not alter basal secretion, which does not require CCK. The three doses of CR-1409 that were used (2, 4 and 8 mg/kg/h) suppressed the protein response to duodenal infusion of oleic acid and significantly enhanced the delayed inhibition normally observed in control rats (-81%, -87% and -88% vs.

Effects of zinc and copper deficiency associated with protein or lipid deficiency on rat exocrine pancreatic secretion.

Copper and zinc are both secreted by the pancreas but are necessary for pancreatic secretion. We have studied the effects of a 4- or 8-week zinc or copper-deficient diet associated with or without lipid or protein deficiency on rat pancreatic secretion after stimulation by secretin, cerulein, or intraduodenal oleic acid. Twenty animals were in the control group; 40 rats were fed a copper-deficient diet (20 copper-deficient only and 20 copper- plus lipid-deficient).