Some Aspects of Maternal Metabolism Throughout Pregnancy in the Conscious Rabbit

Abstract

SummaryStudies of maternal metabolism during pregnancy have focused principally upon the latter half of gestation. However, maternal metabolic adaptations to pregnancy may occur at all stages of pregnancy. To study maternal metabolism throughout pregnancy, we developed a chronically catheterized rabbit model in which animals could be studied under conscious, stress-free conditions when nonpregnant and then serially throughout pregnancy.Anesthesia produced marked hyperglycemia. In contrast, chronic catheterization and daily handling did not affect blood concentrations of glucose, lactate, ketone bodies, or free fatty acids, or food intake. Glucose concentration decreased with pregnancy to a value at term equal to 85% of the prepregnancy value. Lactate concentration rose significantly in the second half of pregnancy but changes in free fatty acids and ketoacid levels were not significant. These results are discussed from a comparative physiologic point of view, emphasizing the unique aspects of rabbit metabolism during pregnancy and the importance of performing such studies under conscious, stress-free conditions.The impact of pregnancy upon maternal metabolism of carbohydrates and lipids has been studied in the rat (14,20), guinea pigs (I I, 37), and man (8,18,30). In these species, most studies were performed over the latter third of gestation. It is probable that the timing and the magnitude ofmaternal metabolic changes during pregnancy may be related to such factors as the growth rate of the fetus and the placenta, the fetal and placental mass and metabolic rate at different stages of pregnancy, and the maternal diet. In particular, animal species with a relatively short gestation that produce a large fetal to maternal mass ratio at term (i.e., guinea pig, 0.50; rat, 0.17; and rabbit, 0.15) are of interest with regard to the maternal metabolic changes which occur during the entirety of gestation.The majority of metabolic studies during pregnancy have involved surgical, anesthetic, and handling stress. In particular, in the rabbit there have been no studies describing maternal metabolism at any time of pregnancy under chronic, stress-free, steady state conditions. The present paper describes our results in developing techniques for chronic catheterization of rabbits prior to pregnancy, permitting metabolic studies in the conscious

Effect of High Levels of Insulin on Glucose Utilization and Glucose Production in Pregnant and Nonpregnant Sheep

“…Elevated maternal plasma levels of chorionic gonadotrophin that increase in late pregnancy in sheep also may add to the inhibition of glucose utilization (10, 1 1). Similar changes in hormonal milieu have been observed in late pregnancy in human (3), rat (7), and rabbit (29) and have been associated with both glucose intolerance and insulin resistance. In the present study, sheep appear to be similar in that high levels of insulin can enhance tissue glucose utilization but to a lesser extent than in nonpregnant fed ewes, indicating that the mechanisms producing the reduced basal glucose utilization rate of the nonuterine tissues in sheep cannot be reversed easily with insulin (at least at the levels and duration achieved in the present study).…”

Changes in Clinical Pathology Parameters During Gestation in the New Zealand White Rabbit

“…Because the rabbits used in the present study were relatively young at the time of mating (16)(17)(18) (59) by affecting bone-specific ALP (15,47). Estrogen (estradiol) levels in pregnant rabbits have been reported to increase during the first 7 days after mating (28) and then remain relatively stable until the last 2-3 days before parturition, when a small increase occurs (8,18).…”

“…Blood samples from 90 nulliparous, nonpregnant New Zealand White rabbits (ages [16][17][18] wk) were drawn at the supplier's facility (Centre Lago, Vonnas, France). These samples were used to create the pretest database against which values recorded during pregnancy were assessed.…”

Alanine and lactate as gluconeogenic substrates during late gestation

“…rabbit f5], guinea-pig f6], human j4,7f and rat [8-l 11, either in the ~stabsorptive state or after an overnight fast. Hence, it has been suggested that gluconeogenesis decreases in the fed pregnant animal during late gestation [5,12,13]. However, we have recently shown that the in vivo rates of gluconeogenes~s from lactate increase &fold in fed pregnant rats at term gestation [14], which represents almost 50% of the glucose utilized by the conceptus [10,14], Nevertheless, decreased operation of the glucose-alanine cycle has been reported to occur in late pregnancy [IS].…”