Neurohormonal control of ecdysteroid biosynthesis by Carcinus maenas Y-organs in vitro, and preliminary characterization of the putative molt-inhibiting hormone (MIH).

Using simple culture techniques, the effects of neurosecretory tissue, sinus gland-conditioned media, and sinus gland extracts upon the biosynthesis of ecdysteroids by Carcinus maenas Y-organs in vitro were investigated. The sinus glands were found to be a major source of a factor which profoundly repressed ecdysteroid synthesis and which did not appear to be species-specific within other brachyurans examined (Liocarcinus, Cancer). It is suggested that the inhibitory factor is produced by the neurosecretory tissues of the medulla terminalis. It is argued that the inhibitory factor is the putative molt-inhibiting hormone (MIH). Partial characterization revealed that MIH is a heat-stable, trypsin-sensitive neuropeptide, eluting on a Sephadex G-50 gel in a range of approximately 6-14 kDa. By consideration of the dose-response characteristics, it is estimated that MIH may be active in the subpicomolar range.