1. Investigación

Una dosis oral de glucosa (2 g/Kg de peso) produjo cambios similares en la glucosa sanguinea de ratas gestantes de 20 dias y virgenes mientras que el aumento en la insulina plasmatica fue mayor en los animales gestantes, indicando resistencia a la insulina. En el presente trabajo se estudia si un ejercicio moderado y aerobio durante la gestación modifica la respuesta a la insulina en la madre. Ratas virgenes y preñadas de 20 días corrieron en una cinta rodante inclinada 10° durante 5 dias/semana a 20 ml mine incremento progresivo hasta 75 min en el dia 20 de ejercicio y/o gestación en que fueron sometidas a un test de tolerancia intravenoso de insulina con 10 IU de insulina porcina/Kg peso. El efecto hipoglucemiante de la insulina intravenosa mostró una mayor respuesta a la insulina en las ratas preñadas ejercitadas con respecto a las no ejercitadas, mientras que no se observa efecto en las ratas virgenes.

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.

To establish the temporal stages at which changes in insulin/glucose interactions may appear during gestation in the rat, unanesthetized animals were subjected to oral glucose tolerance tests (2 g glucose/kg) at days 15 and 21 of gestation and were compared to virgin female controls. On day 15 glucose tolerance is enhanced in the pregnant rat whereas plasma insulin levels are like those in control animals. On day 21 glucose tolerance does not differ between the two groups although insulin is higher in the pregnant animals. Results show 2 differenciated stages of insulin/glucose relationships throughout gestation in the rat with enhanced insulin sensitivity on day 15 and enhanced insulin resistance during late gestation. It is suggested that these changes contribute to the anabolic tendencies of the mother during mid gestation and her catabolic condition during late gestation.

To determine whether aerobic training throughout gestation modifies glucose tolerance, female Wistar rats were mated or kept nonpregnant and run or not on a 10° slope treadmill for 5 days/week at 20 m/min, starting with a 20-min run, and with a progressive daily increase of 5 min, reaching a 75-min run on the 20th day of protocol or gestation. The exercise protocol did not modify food intake, maternal and fetal weights, litter size or blood lactic acid levels. The rise in blood glucose after an oral glucose load (2 g/kg bodyweight) did not differ between trained and untrained nonpregnant rats but was lower in trained than in untrained pregnant rats. In the untrained rats the rise in plasma insulin levels after the glucose load was much greater in pregnant than in non pregnant rats; in trained rats this difference between groups was attenuated by the greater effect of exercise decreasing the plasma insulin response to the glucose load in pregnant than in nonpregnant rats. Thus, an aerobic exercise protocol that does not modify the outcome of pregnancy does significantly reduce the altered oral glucose tolerance in pregnant rats and only has a minor effect in non pregnant rats.