|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1995 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1994 : ¥700,000 (Direct Cost : ¥700,000)
In screening the luminal action of hormones in isolated perused rabbit cortical collecting duct (CCD), distinct luminal action of prostaglandin E2 (PGE2) on transepithelial voltage (Vt) was found. Thus, we first addressed to exploration of the effect of luminal PGE2. As the results : 1) InM to 1muM luminalPGE2 depolarizes Vt after transient hyperpolarization. 2) the Vt change induced by luinal PGE2 is specific, since the luminal action is preserved in the presence of basolateral PGE2, or luminal vasopressin. 3) Furthermore, prostaglandin 12 which mimic the action of PGE2 when administered to the basolateral side fails to induce a Vt change from the luminal side.
4) the luminla PGE2-induced Vt change is abolished in the presence of the Na/K ATPase inhibitor ouabain in the bath or the Na channel blocker amiloride in the lumen but not by the K channel blocker Ba in the lumen, and 5) indeed, the lumen-to-bath Na flux is suppressed by luminal PGE2,6) luminal PGE2 also enhances osmotic water permeability to a modest degree.
Taken together, the lumnal action of PGE2 is distinct from that of luminal vasopressin which we have alredy reported in terms of the pattern of Vt change, response to ouabain, and effect on Na and water transport. It is suggested that PGE2 excreted in the urine also regulate the urine production in vivo.
Coming back to the screening of luminal action so fo hormones in the CCD using Vt as the marker, we next found that oxytocine, bradykinin, dopamine and adrenalin have luminal action swhile luminal angiotensin II or adenosine are inert. We are now in the process of characterization of the luminal actions of these hormones and exploratioin of the interactions between basolateal and luminal vasopressin and PGE2.