Glucose and insulin tolerance tests in the rat on different days of gestation.

Abstract

To study insulin/glucose relationship during gestation, rats were studied on days 6, 12, 15, 18, 20 or 21 of presnancy and the results were compared to values in sex.matched virgin control rats. Blood glucose levels were decreased on days 20 and 21 of gestation whereas plasma insulin levels appeared decreased on days 6 and 12, unchanged on day 15 and enhanced on days 18. 20 and 2L of gestation. Total pancreas insulin content was already augmented on day 6 of gestation and continued to increase with gestational time. \Vith the exception of an increase in tbe 6-day.pregnant rats 22.5 min after an oral glucose toad, blood glucose levels did not differ between 6• or 12-day.pregnant rats and virgin controls although plasma insulin levels reached higher values on these days. However. in the 15-day-pregnam rats, glucose tolera!lce after the glucose load was enhanced while plasma insulin levels did not differ from those in virgin rats during the first 30 mjn. In the IS-day-pregnant rat blood glucose was more increased but plasma insulin did not differ after the glucose load when compared to virgin rats, whereas 20. or 21-day-pregnant rats showed a gJucose tolerance similar to that of virgin rats but their insulin levels shonly after the glucose load were higher. The hY'I.»" glycemic response lo a high intravenous dose of insulin was decreased in 12-, 18-. 20- and 21-day-pregnant rats. TI,erefore, whereas in both the 6- and 12-day-pregnant rats there is an enhanced 13-,celJ response to the glucose insulinotropic effect and insulin responsiveness is reduced in J 2. day-pregnant rats. the 15-day pregnam rat is in a transitory stage where both insulin sensitivity and the J},-ccll response return to non pregnant vaJ. ues. Ho\•.revcr. from 18 da)'S of gcslation on, there is an intense insulin• resistanl condition which is only partially compensated by an enormous accumulation of insuJin in the pancreas followed by a faster and larger insulin release after a glucose load.