Effect of epidermal growth factor on acid and pepsinogen secretion by rat isolated stomach cells stimulated with forskolin

Abstract

Ihisioti o/'Hio/o&y, l ' i i i r r t~i i i~~~~r i t i~~i r lScicticvs Iti.siitirtc, A.stoti Utiitwsity, Astori 7i.iirtigIc. Hirt)iitigiiirtti 114 7E7; U. K .Epidermal growth factor (EGF ) from mouse submaxillary glands is ;I polypeptide o f hi, 00.15 which stimulates cpithelial cell proliferation ;ind which inhibits gastric acid secretion both iti iii.o I I I a n d iri ~i i r o 12. 3 I . Inhibition of pepsinogen secretion by k<iF has been observed iti t i i v 1 4 I . but this effect could be secondary t o an inhibition of acid secretion. T h e mechanism by which EGF inhibits acid sccrction induced by histamine may involve ;I decrease in the cyclic A M P content ofthc parietal cell 131.T h e intention o f this work wiis to investigate whether E G F could also inhibit acid secretion induced by forskolin which acts directly t o xtivatc adcnyl;itc cyclase. If such an cffcct were found then ;I comparison could be made with the cffcct o f EGF o n forskolin-stimulatctl pcpsinogen secretion.Stomach cells were isolntctl from the rat fundus by pronase digestion a n d intermittent calcium chclation 15 I . T h e accumulation of the weak base aminopyrine was used iis a n index o f acid secretion ( 5 1 , and pcpsinogen secretion was determined by measuring the ability o f supernatant samples t o hydrolysc acid-denatured hacmoglobin [ 6 I . Forskolin produced ;I dose-related increase in the aminopyrine ;iccumulation ratio. which was 49 * 6 (mean f S.F M. from I7 batches o f cells) in the presence o f 50 pM-forskolin. Responses to I h, 5 and I0 pM-forskolin were 13. 33 and 5 S ' L of that obtained with 5 0 pM-for4wlin. L G F ( 7 0 0 i i~] only inh i bit etl am inopy rinc accu ni ulat ion st imu Iatecl by 1.6 ;ind 5 pM-torskolin. Similar results were ohtainccl in the ptcwncc of I 0 ,icM-cimctitlinc. uhich wiis acldecl to block the effects o f any endogcnous histamine. should it be present. 'l'hc inhibitory action of E<;F against stimulation induced by lo^ concentrations of forskolin wis prevented by the pi-csencc of ~-isobiityl-I -methylxanthinc (0.1 n i M ) a n d by prcincuhntion of the cells for 2 h with pertussis toxin ( 100 iig/mli. Forskolin also produced ;I tlosc-rel:itcd stimulation ol' pcpsinogcn secretion. but its action was not inhibited by 200 n M -t j G t . uhatcvcr the level of the wcrctory response. LIGF ( 7 0 0 I1M) did not affect either biisd aniinopyrine nccumulotion o r lxisal pcpsinogen secretion. An enriched fraction containing greater than XO'% of parietal cells wiis sonicnted a n d was uscd for assay o f adcnylate cyclase 171. Stimulation of adenylate cyclase activity by 5 p w f o r s k o h was 8 1 f 17 ( t i = 4) pmol cyclic A M P formed/ 1 0 min per 10" cells. This stimulation was unaffected by the presence of 200 nM-EGF.T h e mechanism by which E G F inhibits acid secretion induccd by histamine 131 and by forskolin may be similar, because, in both cases, the action of EGF was prevented by prcincubation with pertussis toxin or by the presence of 3-isobutyl-1-methylxanthine. T h e lack o f effect of E G ...

Stepwise Optimization of Inducible Expression System for the Functional Secretion of Horseradish Peroxidase in Saccharomyces cerevisiae

“…Thus, the recombinant microbial synthesis of HRP is an effective alternative. Among plenty of microbial hosts, Escherichia coli was used in the first attempt to express HRP, , but only the renatured HRP from the inclusion body with a lower V max and shorter half-life can be obtained because of the lack of post-translational modification and folding . As for the eukaryotic hosts, successful soluble expression of HRP has been achieved in Saccharomyces cerevisiae (25–41 U/L HRP at shaking-flask level), , Cryptococcus sp.…”