Cellular basis for long-term neuronal adaptation.

1974); (4) decrease in oxidative phosphorylation by the same cells; (5 ) activity only when added to the blood side of the toad bladder and peritubular surface of the isolated nephrone segment. We have found natriuretic factor to be present in greatly increased quantities in both blood and urine in uraemia; hence its rate of production must be increased in uraemia. Moreover, the natriuretic response per nephron to a fixed amount of natriuretic is markedly increased in uraemia, thus indicating that the sensitivity to the factor is increased in uraemia (Fine et al., 1976a,b). Recent attempts to purify natriuretic factor are as follows. (1) The active fraction from Sephadex G-25 chromatography was further fractionated by using high-pressure liquid chromatography with cation-exchange H70 (Hamilton). Six fractions were obtained (Fig. la). Only the first, F(l), inhibited the short-circuit current (22.2+4.1%; six experiments). The others has no significant effect on the short-circuit current. (2) By re-chromatography of fraction F(l) in the same system under different conditions of elution, six separate fractions (A-F) were identified (Fig. Ib). Only two of these (A and B) inhibited the short-circuit current (15.1k2.1 and 11.2+2.2%; 1 1 experiments). Both were fluorescent, but only fraction B contained fluorescamine-sensitive primary amines. These data on the isolation of natriuretic factor with high-pressure liquid chromatography system seem promising. The use of fluorescamine in the detector system makes the procedure very sensitive (Bohlen et al., 1975). By using discontinuousstream sampling of the column effluent, sample consumption is minimized. Typically, 5-10% of the column eluate is used for monitoring, and the remainder can be used for bioassay or other analytical purposes (Radhakrishnan et al., 1977). To date the most highly purified biologically active peptide-containing fraction, has the following characteristics: it contains no free amino acids before hydrolysis, but neutral and acidic amino acids (mainly glycine) after hydrolysis; it is non-volatile, lipid-insoluble, temperature-resistant and inactivated by pH 10.5. These investigations were supported in part by U.S. Public Health Service grants 2PO1 AM 16281 and R01 AM 19822. Bohlen, P., Stein, S., Stome, J. & Udenfriend, S. (1975) Anal. Biochem. 67,438445 Bourgoignie, J. J., Klahr, S. & Bricker, N. S. (1971) J. Clin. Znoest. 50, 303-312 Bourg0ignie.J. J.,Hwang, K. H.,Ipakchi,E. &Bricker,N. S.(1974)J. Clin.Znoest.53,1559-1567 Epstein, M., Bricker, N. S. & Bourgoignie, J. J. (1978) Kidney Znt. 13, 152-158 Favre, H., Hwang, K. H., Schmidt, R. W., Bricker, N. S. & Bourgoignie, J. J. (1975) J. Clin.