Serum-induced inhibition of isotonic fluid absorption by the kidney proximal tubule I. Mechanism of inhibition

Isotonic reabsorption by the rat kidney proximal tubule was drastically inhibited after less than 2 min intraluminal perfusion with fresh sera from rat (both homologous and autologous), cat, rabbit and human, but not with sera from mouse and guinea pig. The inhibitory factor in serum in a heat (56° C for 30 min) and storage (4°C for 2–5 days) labile macromolecule (mol. wt 50 000) and requires Ca²⁺ for its effect. The cellular electrical potential difference of the proximal tubular cells was irreversively destroyed and intraluminally perfused trypan blue dye incorporated into the tubular cells after the intraluminal perfusion with serum for 2 min. These observations suggest that lysis of the proximal tubular cells is the mechanism for serum-induced inhibition of proximal tubular isotonic reabsorption.     

Induced optical activity in poly-L-lysine-methyl orange system

The absorption and cicular dichroism spectra of the complex of poly-L -lysine (PLL) in the random coil form with methyl orange (MO) have been measured in aqueous solution. A new absorption band is observed at the shorter wavelength compared with that of the free dye. Although MO does not show a formation of dimer or aggregation with an increase in concentration, circular dichroism bands are observed at the wavelength corresponding to the wavelength of the new absorption band. These induced circular dichroism bands may arise from the dimeric MO molecules bound to PLL in the random coil form. The main contribution to the interaction between MO molecules is shown to be the electro static interaction. The observed circular dichroism spectra and the configuration of dimeric MO molecules bound to PLL can be explained by the dipole couping mechanism.