PT  - JOURNAL ARTICLE
AU  - G Sprakties
AU  - H J Macherey
AU  - K U Petersen
TI  - Secretin and somatostatin as modulators of electrolyte transport in guinea pig gallbladder epithelium.
DP  - 1993 Apr 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 273--280
VI  - 265
IP  - 1
4099  - http://jpet.aspetjournals.org/content/265/1/273.short
4100  - http://jpet.aspetjournals.org/content/265/1/273.full
SO  - J Pharmacol Exp Ther1993 Apr 01; 265
AB  - Effects of secretin and somatostatin on electrolyte transport by guinea pig gallbladder epithelium were investigated in vitro. Tissues were mounted in Ussing-type chambers and continuously short-circuited to measure tissue conductance, short-circuit current (Isc) and transepithelial voltage. Unidirectional fluxes (from mucosa to serosa: Jms; from serosa to mucosa: Jsm) of Na+ and Cl- were determined simultaneously by using tracer techniques and those of HCO3- by pH-stat titration. Serosal addition of secretin caused concentration-dependent increases in tissue conductance, Isc and (lumen-negative) transepithelial voltage. At 1.3 x 10(-8) M, secretin raised net HCO3- secretion by 1.5 mumol/cm2/hr, due to inhibition of Jms (from approximately 1.2 to approximately 0.7 mumol/cm2/hr) and stimulation of Jsm (from approximately 3.7 to approximately 4.7 mumol/cm2/hr). The associated increase in Isc by approximately 3.8 mumol/cm2/hr (up from approximately 0.5 mumol/cm2/hr) was not different from net HCO3-secretion (approximately 4 mumol/cm2/hr). Neither Na+ nor Cl- net fluxes accounted for secretin-induced Isc, both being absorbed at equal rates (Na+: approximately 2.7, down from approximately 4.6 mumol/cm2/hr; Cl-: approximately 2.5, down from approximately 6.4 mumol/cm2/hr). Secretin caused a 10-fold rise of luminal efflux of cyclic AMP that was mitigated by somatostatin, added at 6 x 10(-7) M to the serosal bath. Somatostatin inhibited secretin- and prostaglandin E1-induced Isc, but was ineffective in tissues stimulated with 8-Br-cyclic AMP. It partly reverted the effects of secretin on JmsHCO3 and JsmHCO3, but had no effects in untreated tissues. Our data indicate that secretin converts HCO3-secretion from an electroneutral into an electrogenic process and blocks part of NaCl absorption.(ABSTRACT TRUNCATED AT 250 WORDS)