Effects of exercise and pregnancy on amino acid absorption by the rat small intestine

Active transport rates have been shown to be subject to change. They are likely to change In the face of different environmental conditions, pregnancy, and the additive condition of exercise and pregnancy. Studies were undertaken to elucidate the effects of pregnancy, exercise, and a combination of both on active transport In terms of net serosal accumulation of amino acids by the gut. In addition, the effects of exercise on pregnancy were evaluated by comparing conceptus, body, and adrenal gland weight changes of exercised pregnant rats with non-exercised pregnant rats. Groups consisted of 7, 14, and 21-day pregnant rats; 7, 14, and 21-day pregnant rats exercised on days 0-6, 7-13, 14-20, and 0-20 of gestation respectively, 7 and 21-day exercised rats, and control rats for all durations. Net serosal accumulation studies were performed using the gut sac method of Wilson and Wiseman as modified by Lawrence and Lawrence. Amino acids employed in these studies were alanine, proline, lysine, and glutamic acid, and the amino acid analogue alpha-aminoisobutyric acid (AIB). In general, glutamic acid and AIB were found unsuitable for net serosal accumulation studies of rat small Intestine. Lysine net serosal accumulation Increased In the 7-day pregnant rat and this Increase was found to be due to an Increased active transport rate of this substrate by the gut. Proline net serosal accumulation decreases in the 21-day pregnant group and this decrease was found to be due to a decreased intestinal active transport rate by this group. The accumulative effect of pregnancy and exercise Increases net serosal accumulation of alanine in the second trimester and decreases it in the third trimester. This was believed to be due to an Increase and decrease In active transport, respectively. Exercise during the entire period of pregnancy appears to allow transport mechanisms to adapt, or at least to remain normal. Exercise Incurred during any one trimester of pregnancy, and lasting for the duration of that trimester only, was detrimental to the rat In nearly all parameters measured. However, exercise throughout the term of pregnancy was beneficial In that no detrimental effects were noticed while maternal tissue weight decreased and active transport rates remained unchanged. Pregnancy causes large, and exercise plus pregnancy causes smaller body weight Increases. The smaller Increase In body weight of one trimester, exercised pregnant animals, was due to less weight gained by maternal tissues and the conceptus. The body weight gain of pregnant animals exercised for the duration of pregnancy was found to be very similar to that of pregnant non-exerclsed animals. This was due to a small weight gain In maternal tissues while the conceptus weight remained unchanged.