No abstract

Colchicine, vinblastine, podophyllotoxin, and cytochalasin B inhibit the action of vasopressin and cyclic adenosine monophosphate on osmotic water movement across the toad bladder. The findings suggest that microtubules, and possibly microfilaments, play a role in the action of vasopressin, perhaps through involvement in the mechanism of release of secretory material from the bladder epithelial cells.

No abstract

Melting point depression was used as an index of the water potential of rat tissues and serum. Organs removed from anesthetized rats w~re immediately frozen in liquid nitrogen and ground with mortar and pestle. Aliquots of the resulting frozen powder were suspended in chilled liquid silicone. While the suspension was vigorously stirred and warmed at a constant rate, the temperature of the melting mixture was measured.The melting curves of rat muscle, liver, heart, and brain were not significantly different from those of rat serum. The melting curve depression of whole kidney was greater than that of serum; this was demonstrated to be due to hypertonicity of the renal medullary area alone. It was demonstrated that autolysis will rapidly increase the depression of the melting curve of tissue. It is concluded that within the limits of the method used the melting point depression, and hence the water potential, of intracelhlar and extracenuiar fluids is the same.