AJP - Renal Physiology, Vol 258, Issue 6 1561-F1568, Copyright © 1990 by American Physiological Society
AVP reduces transepithelial resistance across IMCD cell monolayers
D. R. Mishler, J. A. Kraut and G. T. Nagami
Medical Service, Veterans Administration Medical Center, West Los Angeles 90073.
The inner medullary collecting duct (IMCD) is an important site of action
for arginine vasopressin (AVP). To examine the mode of action of AVP in
this segment, we measured the change in transepithelial resistance of
cultured rat IMCD cells grown to confluence on collagen-coated Millicell
culture plate inserts in response to AVP. Resistance was measured by use of
an EVOM voltage-ohm meter. AVP at 10(-11)-10(-8) M caused a fall in
resistance of 6.9 +/- 1.3 to 14.0 +/- 1.4 omega.cm2 (P less than 0.05 to
less than 0.01 vs. no AVP), which was reversed by removal of AVP or
addition of 10(-6) M amiloride. Pretreating the apical surface of IMCD
cells with trypsin had no effect on resistance but totally prevented the
antidiuretic hormone-induced fall in resistance. Pretreating the apical
surface with trypsin and amiloride did not prevent the fall in resistance
to AVP. Addition of 10(-9) M AVP or 10(-6) M forskolin increased 2-min
adenosine 3',5'-cyclic monophosphate (cAMP) accumulation by 55 or 96%,
respectively. Stimulation of endogenous cAMP accumulation by forskolin or
the addition of exogenous 8-bromo-cAMP caused no change in resistance. To
examine the relationship between intracellular calcium [( Ca2+]i) and AVP
action, the response of [Ca2+]i to AVP was measured by use of fura-2. AVP
induced no change in [Ca2+]i in IMCD cells in suspension, on glass cover
slips, or on permeable supports. Ionomycin (25 nM) increased [Ca2+]i in
IMCD cells and lowered resistance across monolayers, but the fall in
resistance was not blocked by amiloride.(ABSTRACT TRUNCATED AT 250 WORDS)
