Insulin gene expression pattern in rat pancreas during the estrous cycle

Sex steroid hormones influence insulin homeostasis and glucose metabolism, estradiol (E-2) and progesterone (P-4) induce changes in both fasting and p ostprandial insulinemia in rodents, however, insulin gene expression during estrous cycle is unknown. The aim of the present study was to determine an insulin gene expression pattern during the estrous cycle in the rat. Group s of 6 adult rats in each day of the estrous cycle were used. Serum P-4, E- 2, testosterone (T) and insulin concentrations were determined by radioimmu noassay (RIA). A Northern blot analysis was performed to assess insulin gen e expression in pancreatic tissue. We found a marked variation in insulin g ene expression during the estrous cycle. The highest insulin expression was observed during the proestrus day. Interestingly, E-2 and P-4 but not T le vels were correlated with changes in insulin mRNA content. The variations i n serum insulin during the cycle were correlated with its mRNA content in p ancreas. The overall results showed variations in serum insulin and insulin gene expression during estrous cycle of the rat that correlated with circu lating E-2 and P-4 levels. (C) 2001 Elsevier Science Inc. All rights reserv ed.