THE GROWTH OF THE ADRENAL GLAND OF LABORATORY AND FIELD VOLES, AND CHANGES IN IT DURING PREGNANCY

Abstract

In laboratory-bred voles of either sex which weigh more than 22 g, adrenal gland weight remains constant as body weight increases. Females have larger adrenals than males, this difference becoming accentuated after animals have become sexually mature. Adrenals of pregnant voles are larger than those of nulliparous animals, but do not increase in weight with increase in body weight. However, adrenals of field males and pregnant field females increase in weight with increase in body weight.Difference in weight between adrenals of male and female laboratory voles could be due to a reduction in size of the X zone of the adrenal cortex in males, brought about by androgens. But since, in the field, adrenal weight increases with body weight, it is supposed that further factors (e.g. effects of social interactions) are influencing the adrenal cortex of field animals.The increase in size of the adrenals of voles in their first pregnancy is associated with an increase in the size of the X zone. This enlargement itself increases as pregnancy proceeds and could be caused by a rising level of L.H. and (or) a decreasing titer of androgens.