The effects of N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, on the vagal cholinergic increase in gastric mucosal blood flow (GMBF) and acid secretion induced by intracisternal injection of the thyrotropin-releasing hormone (TRH) analogue, RX 77368, were studied. GMBF and acid secretion were measured simultaneously by the hydrogen gas clearance technique and titration of gastric perfusate in urethan-anesthetized rats. RX 77368 (30 ng) injected intracisternally stimulated gastric acid secretion and GMBF for 90 and 180 min respectively. GMBF was increased from basal 63 +/- 4 to 166 +/- 14 ml.min-1.100 g-1 at 60 min postinjection. L-NAME (3 mg/kg) injected intravenously 15 min before RX 77368 completely prevented the increase in GMBF induced by the TRH analogue, whereas the acid response was not modified. The effect of L-NAME was reversed by L-arginine but not by the stereoisomer D-arginine. These results show that the increase in GMBF, but not the stimulation of acid secretion, induced by central vagal activation is mediated through a product of L-arginine-NO pathway.

No abstract

The fate of palmitoyl-lysophosphatidylcholine (lysoPC) incorporated into the membrane of intact human erythrocytes from a medium was investigated under nonhemolytic conditions at 37 degrees C by means of 14C-labeled tracers. The lysoPC was first incorporated into the outer half of the membrane lipid bilayer and then gradually translocated into the inner half during the incubation. At the same time it was metabolically converted into phosphatidylcholine (PC) and free fatty acid (FFA) plus glycerophosphorylcholine by the actions of acyltransferase and lysophospholipase, respectively. The half times of the conversion were about 14 h, while the value of 0.5 h was obtained when the half time was measured with the hemolysate of the lysoPC-loaded erythrocytes. Chymotrypsin treatment of unsealed ghosts caused a definite decrease in lysophospholipase activity, while similar treatment of resealed ghosts did not. This together with other evidence already reported in the literature suggests that both lysophospholipase and acyltransferase may be located in the inner surface of the membrane. The above findings strongly suggest that the most of the lysoPC loaded to the membrane is gradually translocated from the outer to the inner half of the bilayer and soon converted to either PC or FFA.

Abstract-Studieswere performed to characterize ethacrynic acid (EA) highly sensitive Mgt+-ATPase isolated from microsomal fractions of the rat brain. The functional molecular sizes of the EA highly sensitive and EA less sensitive Mgt+ ATPases, estimated by a radiation inactivation method, were 480 and 80 kDa, respectively.An anion transport inhibitor, 4-acetamido-4'-isothiocyanostilbene 2,2'-disulfonic acid (SITS) inhibited the EA highly sensitive Mgt+-ATPase activity. The type of inhibition was uncompetitive with respect to ATP, and the inhibition was suppressed by anions such as CI-, Br and I-. Chloride ions stimulated enzyme activity with an increase in Vma ,X, but not in Km, for ATP. Anions tested also increased the enzyme activity in the following order of decreasing potency: CI-> Br->CH3000-=I->S042-=HC03->S032-.These results suggest that EA highly sensitive Mgt+-ATPase is a relatively large molecule with anion-sensitive sites that affect the ATP hydrolyzing activity and the SITS binding capacity through anions, with CI being the most potent.