Effects of treatment with progesterone and oestradiol-17 beta on the endocrine pancreas in ovariectomized rats: ultrastructural variations in the B cells.

The effects of progesterone and/or oestradiol treatment on the ultrastructural appearance of the pancreatic B cells has been studied in ovariectomized Wistar rats. A morphometric examination of the numberical density of dark and high granules in the B cells was therefore performed in each group of experimental rats as well as in control (olive oil-injected) rats. In the oestradiol-treated rats, and especially in the rats with combined oestradiol/progesterone treatment, the proportions of light and dark granules in the pancreatic B cells changed, compared with control values, in favour of the light granules. This increase in light granule content was comparable to changes in B cells during a pregnancy and it is suggested that the secretory activity of the B cells increases during pregnancy in a manner similar to that seen during oestradiol treatment.