Repeated pregnancy without lactation: effects on maternal glycemic control, pregnancy outcome, carcass composition, and fat distribution in rats.

Repeated pregnancy without lactation in rats has been reported to produce permanently elevated carcass fat mass and hyperplasia in subcutaneous fat depot. In the present study, the pregnancy outcome, intravenous glucose tolerance ability (IVGTT), and carcass composition were further examined in Osborne-Mendel rats. Female rats were divided into pregnancy-lactation (PL), pregnancy-no lactation (PNL), and control (CON) groups. Half of the rats were killed after three pregnancy/lactation cycles, whereas the rest were given a 12-week rest period before killing. It was found that rats in PNL group had fasting hyperglycemia and insulin insensitivity during the third pregnancy (P less than or equal to .05), elevated spontaneous abortion rate (P less than or equal to .05), and elevated subcutaneous fat content (P less than or equal to .01) relative to that of PL rats or CON rats. After a 12-week rest period, a significant increase in subcutaneous fat cell number was also observed in PNL rats. PL rats, on the other hand, have significantly elevated internal/subcutaneous fat ratios (P less than or equal to .05), both immediately after weaning and after the 12-week rest period. The significance of this change is not yet known.