title: Functional segmentation of the rabbit distal tubule by microdetermination of hormone-dependent adenylate cyclase activity.
abstract: Rabbit distal convoluted tubules (DCT) microdissected from collagenase-treated kidneys were observed to contain up to four portions of a different appearance under stereomicroscopic examination: (1) a DCTa portion (generally very short), located right after the macula densa (MD) and resembling the portion of the limb (CAL) located before the MD; (2) a constant, "bright" portion, DCTb; (3) a constant, "granular" DCTg portion which, in most DCT, is connected to a portion of the collecting tubule of a similar "granular" appearance (CCTg); (4) many DCT having contacts with the kidney capsule in the superficial cortex were observed to contain an additional portion of a "light" appearance, DCTl, resembling the portion of the collecting tubule (CCTl) to which these superficial DCT are always branched. The hormone-dependent adenylate cyclase (AC) contained in these different portions was investigated by sectioning microdissected distal structures into successive samples according to the above-mentioned criteria, and by measuring with the help of a previously described micromethod, the enzyme activity contained in each single sample under one of the following conditions: control, parathyroid hormone. (PTH l U/ml), vasopressin, (AVP 10(-6)M), isoproterenol (10(-6)M), fluoride (5 X 10(-3)M). Highly significant and reproducible AC stimulations by these hormones were obtained for the following portions, respectively: DCTa, DCTg and CCTg with PTH; DCTl and CCTl with AVP; DCTg, CCTg and CCTl with isoproterenol. From these data, it is concluded that (a) the distal convoluted tubule can no longer be regarded as a single well-defined functional structure; (b) DCTa is actually a short CAL portion extending beyond MD, (c) DCTg and CCTg are two portions of a same functional segment; (d) similarly, DCTl belongs to the functional segment mainly constituted by CCTl; and, finally, (e) DCTb is the only functional segment which is entirely located in the distal convoluted tubule, i.e., included between the macula densa and the first branching with another tubule.
mesh_terms: D000262:Adenylyl Cyclases / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D005459:Fluorides / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007672:Kidney Cortex / Q000648:ultrastructure; D007684:Kidney Tubules / Q000201:enzymology*; D007686:Kidney Tubules, Distal / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011817:Rabbits; D013268:Stimulation, Chemical; D014667:Vasopressins / Q000494:pharmacology*
chemical_list: D010281:Parathyroid Hormone; D014667:Vasopressins; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D005459:Fluorides