Hormones and the stimulated sodium transport in cecum hypertrophy

Sodium transport per unit tissue is stimulated in dietetically produced cecum hypertrophy of the rat. Presumably this reflects an adaptive process. The possibility was tested whether transport adaptation was mediated by hormones, particularly by the pituitary-adrenal system, Cecum hypertrophy was induced by dissolving polyethylene glycol in the drinking water, and cecal sodium and water net absorption was measured in vivo. In both the adapted and normal mucosa, sodium and water absorption per unit macrosurface or dry weight was increased by aldosterone and decreased by adrenalectomy, hypophysectomy and volume expansion while the decrease following adrenalectomy was reversed by cortisol and the absence of antidiuretic hormone in hereditary diabetes insipidus rats had little effect on absorption. However, none of the test conditions abolished the relatively larger absorption of the adapted compared to the normal mucosa. It is concluded that the hormonal effects were additive but not causally related to transport adaptation.