Ca(2+) influx through the basolateral- and luminal membranes of colonic epithelium in neonatal rats.
In this study, the short-circuit currents ( I(sc)) of electrolyte absorption and secretion in neonatal and adult rat colonic mucosa were compared and the role of Ca(2+) influx through luminal membranes examined in relation to the replenishment of intracellular Ca(2+) stores in colonic crypt cells. Neonatal tissues displayed higher amiloride-sensitive I(sc) and larger increases of electrogenic Cl(-) secretion in response to an increase in cytosolic [Ca(2+)] ([Ca(2+)](c)) or cAMP than found in adult colonic epithelium. Ca(2+)-mediated Cl(-) secretion as reflected in the I(sc) responses to carbachol ( I(sc,CCh)) showed milder "run-down" in neonates than in adult rats. We then employed the relatively stable I(sc,CCh) of the neonatal colon to investigate the polarity of Ca(2+) entry pathway after muscarinic stimulation. Repetitive stimulation with CCh under Ca(2+)-free conditions emptied the intracellular Ca(2+) stores and abolished the I(sc,CCh). Re-adding Ca(2+) to the basolateral perfusate rapidly restored I(sc,CCh) (about 71% of control in 10 min). In contrast, after re-adding Ca(2+) to the luminal perfusate only, the recovery of I(sc,CCh) took much longer and was incomplete, recovering to only 28% of control after 30 min. Recovery was accelerated by increasing [Ca(2+)] in the luminal perfusate (5 mM) and blocked by the presence of Gd(3+) (100 microM) in the luminal perfusate. The above results suggest that, in addition to the predominant role of Ca(2+) entry through the basolateral membrane, the influx of Ca(2+) through luminal membranes might also play a role in the Ca(2+) homeostasis of colonic epithelial cells.
Kim
Soo Jeong
SJ
Department of Physiology, Sungkyunkwan University School of Medicine, Changan-Gu, Cheon-cheon-dong 300, 440-746 Suwon, Korea.
Nam
Joo Hyun
JH
Woo
Ji-Eun
JE
Kim
Sung Joon
SJ
Rhee
Poong Lyul
PL
D000367:Age Factors; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D018679:Cholinergic Agonists / Q000494:pharmacology; D002839:Chromans / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000033:anatomy & histology / Q000378:metabolism*; D004232:Diuretics / Q000494:pharmacology; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology
D018679:Cholinergic Agonists; D002839:Chromans; D004232:Diuretics; D026902:Potassium Channel Blockers; D013449:Sulfonamides; C103474:6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethylchromane; D005576:Colforsin; D000584:Amiloride; D002217:Carbachol; D002118:Calcium