Search

The effects of muscarinic ligands on acid secretion were examined by estimating the accumulation of [ 14 C]aminopyrine in gastric glands isolated from guinea pigs. The accumulation of [ 14 C]aminopyrine in the presence of 0.1 mM histamine was potentiated by 1 μM carbachol but suppressed by 1 mM. These two effects of carbachol were abolished by atropine, pirenzepine and AF-DX 116. Assuming that the binding of carbachol to one site (Site 1) increases [ 14 C]aminopyrine accumulation but its binding to the other site (Site 2) reduces [ 14 C]aminopyrine accumulation, we analysed the dose-response curves for the carbachol effects in the absence and presence of different concentrations of atropine, pirenzepine and AF-DX 116. The dissociation constants determined for these ligands at Sites 1 and 2 were as follows: carbachol, 0.28 and 7.1 μM; atropine, 0.28 and 0.54 nM; pirenzepine, 45 and 560 nM; and AF-DX 116, 380 and 4400 nM, respectively. The binding of [ 3 H]N-methylscopolamine to the gastric glands indicated the presence of two populations of binding sites with different affinities for the above ligands, other than atropine. The apparent dissociation constants, which were estimated by analysing the displacement curves for [ 3 H]N-methylscopolamine binding, were as follows: carbachol, 0.18 μM (10%) and 31 μM (90%); atropine, 1.24 nM; pirenzepine, 15 nM (16%) and 220 nM (84%); and AF-DX 116, 370 nM (10%) and 2970 nM (90%). These results suggest that there are two kinds of muscarinic acetylcholine receptors in the guinea pig gastric gland, one potentiating and the other inhibiting the acid secretion induced by histamine.

A family with a complete deficiency of lactate dehydrogenase M-subunit was investigated. The propositus was an 18-year-old male who complained of exertional pigmenturia and easy fatigue. Marked discrepancy was observed in the ratio between creatine kinase and lactate dehydrogenase (CK/LDH). Electrophoretic analysis of serum LDH isoenzymes of the propositus demonstrated only one activity band of LDH H4. A complete lack of the LDH M-subunit was similarly demonstrated in erythrocytes, leukocytes and in the intermediate vastus muscle. LDH levels in the muscle specimen were markedly decreased in the patient, whereas CK and aspartate aminotransferase were almost the same as in a control subject. LDH isoenzymes of erythrocytes were analyzed in 5 siblings and in the parents. This demonstrated a complete lack of LDH M-subunit in 3 siblings. The ratio between H-subunit and M-subunit (H/M) in erythrocyte LDH suggested a partial absence of the M-subunit in two siblings and in the parents. An abortive increase of blood lactate and a marked increase in blood pyruvate were observed immediately after ischemic work of the forearm, accompanied by an increase in serum creatine kinase and myoglobinuria. The present case represents a newly described form of genetically determined myopathy.

Analog chromatography with glomerular basement membrane isolated from normal and nephrotic rabbits was performed to see if there was a molecular sieving effect by the basement membrane. In a normal glomerular basement membrane column, 125I-labeled human serum globulin and 131I-labeled human serum albumin were eluted at the same position, probably at the void volume of the column. However, 125I-labeled insulin and tritiated water appeared with a delay and gave separated peaks. In nephrotic glomerular basement membrane, 125I-labeled human globulin, 131I-labeled serum albumin, 125I-labeled insulin and tritiated water gave four distinctly separated peaks in that order. By analogy with Sephadex, the sieving effect of glomerular basement membrane was demonstrated.