Effect of adrenalectomy on the arginase levels of liver, mammary gland and kidney in lactating rats studied by the paired feeding technique.

The liver arginase in the rat decreases following adrenalectomy (Fraenkel-Conrat, Simpson & Evans, 1943; Folley & Greenbaum, 1946; Kochakian & Vail, 1947), and in lactating rats the mammarygland arginase behaves similarly (Folley & Greenbaum, 1946). It is possible that the decline in lactation causedby adrenalectomy (see, e.g., Cowie& Folley, 1947 a) is connected with the decrease in mammary-gland arginase, for there is evidence (Folley & Greenbaum, 1947 a) that this enzyme system plays an important role in the metabolism of the lactating mammary gland. Since adrenalectomy is often followed by a marked reduction in food intake (see Ingle, 1944), it is important to find outwhether the depressed tissuearginase levels characteristic of adrenalectomized animals are a primary consequence of the loss of the adrenals or merely a secondary consequence of the post-operative anorexia. Particularly is this so for lactating rats, in which the food intake rises rapidly and steadily over the first 17 days of the lactation period to a value some three times that ofpregnancy, so that even though the effect of adrenalectomy during lactation is to prevent this rise rather than to cause an actual fall, the disparity in food intake between adrenalectomized and intact rats soon becomes very marked (Cowie, Folley, French & Greenbaum, 1948). An investigation of this question by the paired feeding method is described below. The arginase levels ofthe kidney were studied in addition to those of, mammary gland and liver, since Kochakian & Vail (1947) have reported that the kidney arginase, like that of liver and mammary gland, is decreased after adrenalectomy.