Different hormonal target sites along the mouse and rabbit nephrons.

Adenylate-cyclase (AC) activity measurements were performed in the different segments of the mouse nephron. It was found that: --the medullary portion of the thick ascending limb is sensitive to AVP alone. --Three hormones, parathyroid hormone, calcitonin and isoproterenol, stimulate the enzyme activity located in the "bright" and "granular" portions of the distal convoluted tubule. The "granular" portion is, in addition, sensitive to AVP. --a single type of collecting tubules is present and every distal convoluted tubule is connected to it. In the cortex, this collecting segment is sensitive to AVP, calcitonin and isoproterenol. In the medulla, it is sensitive to AVP alone. The enzyme sensitivity to hormones was found in the mouse to be different from that previously described in the rabbit; this is particularly true for the distal segments of the nephron. Thus, hormonal segmentation and more over, regulation of physiological function may be different from one species to another.