Time dependent effects of medroxyprogesterone acetate on hepatic ultrastructure in rats.

The present study demonstrates that MPA treatment may alter liver ultrastructure in rats. This was seen as a slight cytoplasmic vacuolization in light microscopy. In electron microscopy the most striking findings were the increase in the size of hepatocytes, the volume of smooth endoplasmic reticulum (SER) and the number of mitochondria. Minor changes in mitochondrial size and structure, and SER outline were also obtained. The amount of rough endoplasmic reticulum was decreased and bleb formation was common. The effect of MPA on liver ultrastructure was time-dependent. The main changes were found in rats receiving MPA daily for seven days. Most of the observed changes disappeared within 17 days after the cessation of the regimen. MPA induced alterations in liver morphology may partly be due to induction phenomenon although the hormonal property of MPA also may play some etiological role.