Volume 50: 359-364, 2001


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Calcium, Carbonic Anhydrase and Gastric Acid Secretion

I. PUSCAS, M. COLTAU1, M. BAICAN2, G. DOMUTA1, A. HECHT3

University of Medicine Oradea, 1Romanian Medical Academy of Sciences, Center for Research and Medical Assistance Simleu Silvaniei, Romania, 2Clinic Wilkenberg, Germany, 3Medical Care Unit, New York, USA

Received February 9, 2000
Accepted September 20, 2000


Summary
Previous data concerning the action of calcium (Ca) on gastric acid secretion (GAS) indicated that calcium ions increase GAS elicited by gastrin released through a vagal mechanism, and also by a direct effect on parietal cells. Our research showed that the stimulating effect of calcium on gastric acid secretion can be antagonized by verapamil administration, which reduces gastric acid secretion . In the present study we followed the effect induced by administration of calcium and Ca-chelating agents (disodium EDTA) on gastric acid secretion and on carbonic anhydrase (CA) activity. We selected two groups of healthy volunteers: Group I (n=21) received a single i.v. dose of CaCl2 (15 mg/kg b.w.), whereas Group II (n=22) received a single i.v. dose of disodium EDTA (5 mg/kg b.w.). We determined blood calcium before and after treatment, gastric acid secretion at 2 hours, erythrocyte CA II activity, and CA IV activity in membrane parietal cells, which were isolated from gastric mucosa obtained by endoscopic biopsy. Assessment of carbonic anhydrase activity was achieved by the stopped-flow method. In Group I calcium administration increased blood calcium, HCl output, CA II and CA IV activity as compared to initial values. In Group II, disodium EDTA reduced blood calcium, HCl output, CA II and CA IV activity as compared to initial values. The results demonstrated that increased blood calcium and GAS values after calcium administration correlated with the increase of erythrocyte CA II and parietal cell CA IV activity, while disodium EDTA induced a reversed process. Our results also show that cytosolic CA II and membrane CA IV values are sensitive to calcium changes and they directly depend on these levels. Our data suggest that intra- and extracellular pH changes induced by carbonic anhydrase might account for the modulation of the physiological and pathological secretory processes in the organism.


Key words
Calcium · Disodium EDTA · Carbonic anhydrase · Gastric acid secretion

 

Reprint requests
Prof. Dr. Ioan Puscas, MD, Center for Research and Medical Assistance , 4775 Simleu Silvaniei, 37 Dunarii Street, Salaj, Romania Fax +40-60-678320. E-mail: ccam@teli.netcompsj.ro

 


PHYSIOLOGICAL RESEARCH
© 2001 by the Institute of Physiology, Czech Academy of Sciences

ISSN 0862 - 8408

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