Long-term effect of prolactin treatment on glucose-induced insulin secretion in cultured neonatal rat islets

Insulin secretion and 45SCa2+ uptake and efflux were studied in neonatal rat islets maintained in culture for 7 or 19 days in the absence or presence of prolactin (PRL). Insulin secretion in response to glucose (G), leucine (Leu), arginine (Arg) and carbachol (Cch) was augmented after 7 and 19 days in culture, compared to basal secretion (G 2.8 mM), in both PRL- treated and control islets. However, the increase in insulin secretion induced by the above secretagogues was higher in islets cultured in the presence of PRL for 19 days. In PRL-treated islets, the 45Ca2+ content after a 5 min incubation in the presence of G, Leu, Arg and Cch was significantly higher than the control only in islets cultured for 19 days. Except with Arg, the 45Ca2+ uptake in PRL-treated islets after a 90 min incubation was also significantly higher than the control only in islets cultured for 19 days. Finally, Leu-induced alterations in the 45Ca2+ efflux were higher in PRL-treated than in control islets cultured for 7 or 19 days. In the absence of external Ca2+, the reduction in 45Ca2+ efflux induced by glucose was also significantly higher in PRL-treated than in control islets. This effect was slightly potentiated after 19 days in culture. These data further support the hypothesis that PRL treatment enhances maturation of the secretory mechanism in neonatal islets. This effect can be potentiated even more if the treatment is prolonged.

Obesity induces upregulation of genes involved in myocardial Ca2+ handling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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 N (G) -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 pEC(50) 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 (K-D ) and maximal number of binding sites (B-max ) 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 B-max for [(3) H]-quinuclidinyl benzilate of approximately 57% in the l-NAME treated group without any significant change in K-D 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 mumol/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.

Ovarian superstimulation using FSH combined with equine chorionic gonadotropin (eCG) upregulates mRNA encoding proteins involved with LH receptor intracellular signaling in granulosa cells from Nelore cows

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Prepubertal exposure to bisphenol-A induces ERα upregulation and hyperplasia in adult gerbil female prostate

Prostate physiology is highly dependent on oestrogenic and androgenic homeostasis. Interferences in this equilibrium, especially in early periods of life, may disrupt the prostate and increase the susceptibility to the development of diseases with ageing. Taking this into account, and considering the increase of environmental chemicals with endocrine-disrupting potential such as bisphenol-A (BPA), this study aimed to evaluate the prostates of adult female gerbils exposed to BPA and BPA plus testosterone from pubertal to adult periods. Morphological, stereological and chemical analyses revealed that long-term BPA exposure, even in environmental dosages, increases the proliferative status of the prostate, increases the number of ERα-positive stromal cells and elicits the development of prostatic hyperplasia in adult female gerbils. Moreover, we also observed that the association with testosterone did not increase the proliferative status of the gland, which shows that low levels of BPA are enough to cause an oestrogenic disruption of the prostate in young adults. This evidence suggests that this oestrogenic endocrine disruptor may increase the susceptibility to prostatic disorders with ageing.

Prostaglandin receptors (EP2 and EP4) and angiotensin receptor (AGTR2) mRNA expression increases in the oviducts of Nelore cows submitted to ovarian superstimulation

Many peptides are responsible for the coordination of muscle contraction, secretion and ciliary beating of the oviduct epithelium to allow the transport of gametes and embryos, including vascular endothelial growth factors (VEGF), prostaglandins (PGs), endotelin-1 (ET-1) andangiotensinII(Ang II). The effect of reproductive biotechnologiesusedto improve embryo yield on oviduct gene expression is poorly understood. Thus, the aim of the present study was to evaluate the effect of ovarian superstimulation on the mRNA expression of the genes encoding the major peptides involved in oviduct contraction in bovine. Therefore, Nelore cows were submitted to P-36 (n = 5) or P-36/eCG (n = 5) ovarian superstimulatory protocols and a control group of cows was not submitted to any superstimulatory protocol (n = 5). The relative expression of VEGF (VEGF, Flk1, Flt1), Ang II (AGTR2, ACE1), ET1 (ET1, ECE1) and PG pathway members (PGES, EP2, EP4, COX1, COX2) was analyzed using real time RT-PCR in each of oviduct segment (infundibulum, ampulla and isthmus). All target genes were expressed in the three segments of the bovine oviduct; however, specific genes were regulated by ovarian superstimulation: EP2 and EP4 receptors mRNA was affected by P- 36/eCG protocol, in the ampulla and infundibulum, respectively; and AGTR2 mRNA was up-regulated by both the P-36/eCG and P-36 protocols in the isthmus. The upregulation of EP2, EP4 and AGTR2 expression in the superstimulated cows suggests a suitable effect of FSH and eCG on bovine oviduct physiology, coordinating the contraction in Nelore cows