The effect of histamine, metiamide and cystic fibrosis factor on the electrophysiological properties of the frog's gastric mucosa [proceedings].

The total active transport of Cl ions across the frog's gastric mucosa 
can be considered as: net Cl- flux (serosa to mucosa) = 
H+ + SSC (short-circuit current), all terms expressed as micromole cm-2 
hr-1. The net chloride flux (Hogben, 1955; Durbin & Heinz, 1958) 
may be divided into two fractions: an acidic one which is 
equivalent to the acid secreted and an electromotive one which accounts 
for the gastric electromotive force. The changes in SCC can accordingly 
be used as a partial index to the activity of the 
chloride pump. Experiments were designed to investigate the effects of histamine, 
metiamide (H2 receptor antagonist), cystic fibrosis (CF) and non-CF plasma on 
the above parameters using the frog's isolated gastric mucosa. The SCC 
and the resistance of the mucosal preparation is measured by means 
of an automatic SCC apparatus (de Jesus, 1977). The H ion 
secretion is measured by pH meter. Results obtained (expressed as mean 
change (delta) plus or minus S.E. of mean) for histamine (10-4 
M) (n = 10) show an initial increase of the SCC 
by 36.94 plus or minus 2.95 microA cm-2 and a parallel 
small increase in H+ output by 0.045 plus or minus 0.003 
micromole cm-2 hr-1. This initial increase in SCC is followed by 
a drop to a steady-state level of 23.62 plus or minus 
2.23 microA cm-2 and also by a large increase in H+ 
secretion 2.26 plus or minus 0.22 micromole cm-2 hr-1. These results 
support the work of Rehm (1961) in that histamine has an 
effect first on the Cl- pump and then on the H+ 
secretion. Metiamide (10-4 M) (n = 12) caused a drop in 
the SCC by 20.16 plus or minus 2.32 microA cm-2 and 
also reduced the acid secretion by 2.21 plus or minus 0.14 
micromole cm-2 hr-1, thus suggesting an effect on the Cl- pump 
as well as on the H+ secretion. Significant differences are shown 
(P < 0.001) between CF and non-CF plasma results. The CF 
plasma (n = 8) increased the SCC by 17.25 plus or 
minus 2.94 microA cm-2 and H+ secretion by 2.38 plus or 
minus 0.43 micromole cm-2 hr-1. Non-CF plasma caused a slight increase 
in SCC by 5.17 plus or minus 1.1 microA cm-2 and 
had little effect on the H+ secretion, 0.34 plus or minus 
0.01 micromole cm-2 hr-1 (n = 8). The effect of the 
CF plasma on the Cl- and H+ mechanism is of interest 
since in cystic fibrosis there is an abnormal increase of Cl- 
and Na+ in the sweat of patients (di Sant Agnese, Darling, 
Perera & She, 1953). 