The hypothalamo-neurohypophysial complex in organ culture: morphologic and biochemical characteristics

Organ cultures of the guinea pig hypothalamo-neurohypophysial complex could be maintained for periods as long as 3 weeks. Morphological studies using conventional light microscopy as well as electron microscopy indicate that neurosecretory cells remain viable during this time. Biochemical studies show that the capability of the cultures to synthesize a normal spectrum of cellular RNA species is impaired during the initial day in culture, but that this capability is restored after 4-5 days. Similarly, protein synthesis proceeds at low levels during initial days of culture, but increases after 5 days. These phenomena appear to be independent of changes in the specific radioactivity of precursor pools and were also observed when outgrowth of non-neuronal cells is inhibited with fluorodeoxyuridine. The content of vasopressin, a product of a specific class of neurosecretory neurons, was found to decrease in the posterior pituitary during 7 - 10 days in culture by 50-70 percent; the levels then plateaued and were maintained for up to 3 weeks. The hypothalamic content of the hormone was relatively constant throughout the culture period. Of most importance was the demonstration that the organ cultures were capable of vasopressin biosynthesis. This capability paralleled the biosynthetic activity of RNA and gross protein metabolism in that there was an initial refractory period of several days duration.