CYTOCHEMICAL EVIDENCE FOR POTASSIUM-DEPENDENT P-NITROPHENYLPHOSPHATASE ACTIVITY IN PAVEMENT CELLS OF RANA-ESCULENTA MESENTERY

Background: We previously reported that during hibernation in Rana esc ulenta, various organs (i.e., skin, urinary bladder, kidney) change th eir osmoregulatory activity, Here, we considered the possible role of the frog mesentery in the ion transport, evaluating morphological and cytochemical (K+-p-nitrophenylphosphatase activity) aspects. Methods: Pieces of mesentery from Rana esculenta collected in their natural env ironment during April, June, October, and January were processed to re veal ultrastructural morphology and K+-p-NPPase activity, using cerium as capture agent. Results: The mesenteric mesothelium contained three types of cells: pavement, mitochondria-rich, and ciliated, Only the p avement cells expressed intense reactivity on the basolateral membrane s and in the adjacent pinocytotic vesicles; some reaction product also was found on the apical membranes, Moreover, morphological and cytoch emical characteristics of the pavement cells appeared to be very seaso nal. Conclusions: The presence of mitochondria-rich cells and ciliated cells, generally found in structures involved in the transport of liq uids, as well as K+-p-NPPase activity and pinocytosis in pavement cell s, is consistent with the hypothesis that frog mesentery may be involv ed in seasonally variable osmoregulation. (C) 1998 Wiley-Liss, Inc.