The Uptake of Tritiated Lysine Vasopressin by Rat and Pig Pituitary Neural Lobes in Vitro

Abstract

Uptake of tritiated lysine vasopressin ([3H]LVP) was studied in halved neural lobes of rats (which had been given either tap water (control group) or 2 % (w/v) NaCl solution as drinking water for 4 days) as well as in slices of pig neural lobe. Uptake of radioactivity into the neural lobes was shown but analysis of the extracts of incubated lobes of both species by ion exchange chromatography showed that very little of it remained in the tissue as hormone. In addition, some radioactivity was associated with trichloroacetic acid-insoluble proteins.After 90 min of incubation, and after correction for the breakdown, the uptake of unchanged [3H]LVP, expressed as a tissue : medium ratio, was 0\m=.\14 \m=+-\ 0\ m=. \ 04 and 0\m=.\09 \ m=+-\ 0\m=.\03 (mean \ m=+-\ S.E.M.) for the saline-treated and control rats respectively, while the tissue: medium ratios for the breakdown product(s) were 6\m=.\47 \ m=+-\ 0\m=.\45 and 5\m=.\50 \m=+-\0\m=.\36. The results suggest uptake of [3H]LVP into the cell with almost complete intracellular breakdown of the hormone.

Distribution of Soluble Proteins in the Mammalian Neurohypophysis and Their Cross-Species Reactivity With Anti-Neurophysin

“…Acting in this manner, the neurophysins may protect the neurohypophysial hormones from the action of posterior pituitary lobe peptidases (Edwards, 1971;Pickup & Hope, 1971;Pliska, Thorn & Vilhardt, 1971). Alternatively, the neurophysins may be remnants of a precursor molecule from which the hormones have been cleaved by the action of enzymes in the perikaryon of the hypothalamic nuclei (Sachs, Fawcett, Takabatake & Portanova, 1969).…”

Uptake of Tritiated Oxytocin Into the Neurohypophysis of the Rat

“…The intracellular concentration of hormone and breakdown products can be estimated by correcting for the breakdown of hormone and by taking into account the extracellular space (this space was determined previously, see Edwards, 1971). …”