Effects of endogenous and exogenous nitric oxide on endothelin-1 production in cultured vascular endothelial cells

The effects of various spontaneous nitric oxide (NO) donors and NO synthase inhibitors on endothelin- production were examined using porcine cultured aortic endothelial cells. NO donors such as (+/-)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-3-hexanamide (NOR 2), (+/-)-(E)-4-ethyl-2-[( E)-hydroxyimino]-5-nitro-3-hexanamide (NOR 3) and (+/-)-N-[(E)-4-ethyl-2-[(Z)-hydroxyimino]-5-nitro-3-hexen-1- yl]-3-pyridine carboxamide (NOR 4) suppressed effectively the release of endothelin-1 from the cells. Endothelin-1 mRNA expression was also attenuated by these compounds. Other NO donors such as 3-[2-hydroxy-1-(1-methylethyl)-2-nitrosohydrazino]-1-propanamin e (NOC 5), 2,2'-(hydroxynitrosohydrazino)bis-ethanamine (NOC 18), s-nitroso-n-acetyl-DL-penicillamine, N-morpholino sydnonimine (SIN-1) had no effects on endothelin-1 production. Endothelial intracellular cyclic guanosine monophosphate (cGMP) levels were significantly increased by all NO donors. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a selective soluble guanylyl cyclase inhibitor, had no effect on the NOR 3-induced decrease in endothelin-1 secretion, although cGMP production was abolished by ODQ. NOR 3 also inhibited endothelin-1 secretion even in the presence of 2-(4-carboxyphenyl)-4,4,5,5-tetrametylimidazole-1-oxyl 3-oxide (carboxy-PTIO), a NO scavenger. NOR 3-induced inhibitory effects on endothelin-1 secretion were abolished by preincubation of the compound in phosphate-buffered saline (37 degrees C, 4 h), a procedure by which about 98% of the parent compound's ability to release NO was lost. NO synthase inhibitors such as N(G)-nitro-L-arginine, N(G)-monomethyl-L-arginine and N(G)-nitro-L-arginine methyl ester (L-NAME) enhanced prepro endothelin-1 mRNA expression and significantly increased endothelin-1 release from endothelial cells. Endothelin-1 secretion was also increased effectively by carboxy-PTIO or ODQ. When the cells were exposed to L-NAME with carboxy-PTIO or ODQ, no significant further increase in endothelin-1 release was observed. These results suggest that endogenous NO inhibits endothelin-1 production through guanylyl cyclase/cGMP-dependent mechanisms. In contrast, it seems unlikely that exogenous NO has an inhibitory effect on endothelin-1 production in endothelial cells. NOR compounds inhibit endothelin-1 production perhaps through NO/cGMP-independent mechanisms, i.e., through an unknown effect of the parent compound itself.

Quantitative analysis of a novel pregnancy-associated protein in trophoblastic diseases, normal pregnancy and healthy female subjects

By means of the Laurell rocket technique, a novel pregnancy-associated protein was measured in the serum of patients with trophoblastic diseases as well as in pregnant women. In 52 normally-menstruating women, the serum levels were below the detection limit in 40 (76.9%); 50 women (96.2%) had levels of less than 2.0 U/ml, and none had levels above 2.1 U/ml. Of 25 patients with a hydatidiform mole, 23 (92.0%) had elevated levels (greater than 2.2 U/ml). In 84 healthy pregnant women, the levels rose from being undetectable before 5 weeks to a plateau in the second trimester. The results suggest that the appearance of this protein in serum is associated with trophoblastic activity.

Measurement of the alpha 2 component of a novel oncodevelopmental antigen by a rapid electroimmunoassay

A method was required for the quantification of a novel oncodevelopmental antigen which increases in the serum of pregnant women as well as patients with ovarian cancer. The native antigen is composed of two components having alpha 2 and beta electrophoretic mobilities. An assay method, involving electroimmunodiffusion according to Laurell, was developed for the measurement of the alpha 2 component of the antigen. The method is sufficiently sensitive to determine significant differences in the levels of antigen in the serum of non-pregnant and pregnant subjects, and patients with ovarian cancer. In addition to routine quantitation, the technique will also be an indispensable analytical tool in the purification of the protein.