Galactogen synthesis-stimulating factor in the slug, Limax maximus: cellular localization and partial purification.

Galactogen synthesis in the albumen gland of the slug Limax maximus is under direct endocrine control [J. van Minnen, J. Wijdenes, and P. G. Sokolove (1983) Gen. Comp. Endocrinol. 49, 307-314]. The present results show that dorsal body cells (DBC) present throughout the connective tissue around the circumesophageal brain are the major cellular source of a galactogen synthesis-stimulating factor (GAL-SF). The amount of GAL-SF varies during sexual maturation of L. maximus (a protandrous hermaphrodite): it is low when animals are immature and reaches a peak in the late female phase when the animals prepare to lay eggs. The morphology of DBC also changes during maturation. DBC are small and release little secretory product in immature and early male-phase animals; release is higher and DBC are larger in late female-phase animals. Gel filtration of homogenates of cerebral ganglia on Sephadex G75 yields one peak of GAL-SF activity with an estimated Mr of 4000-7000 Da. Subsequent anion exchange chromatography showed that GAL-SF could be eluted with a linear NaCl gradient; GAL-SF was found in fractions with a NaCl concentration between 0.04 and 0.07 M.