METABOLIC ANTAGONISTS AND PROLONGED SURVIVAL OF SCALE HOMOGRAFTS IN FUNDULUS HETEROCLITUS

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Abstract
Homotransplantation of pigmented scales in teleost fish is normally followed by an inevitable immunological response by the host against the grafts. Manifested by the microscopically visible destruction of melanophores in the foreign scales, this temperature-dependent reaction occurs in 3 days at 28CC, 5-6 days at 21[degree]C and 14-16 days at 14[degree]C. It is not adversely influenced by splenectomy or hypophysectomy of the host, nor by daily injections of 0.1 ml of 1% trypan blue. Daily intraperitoneal injections (1-2 mg in 0.1 ml distilled water) of antagonists of nucleic acid synthesis (5-fluorouracil, 5-deoxyribofluorouridine and 6-mercaptopurine) prolonged survival of homografts up to 7 days at 28[degree]C by which time the fish died of the lethal effects of the drugs. Injections of 2 mg of 6-fluoro-hydrocortisone and delta-1-hydrocortisone likewise enhanced survival of homografts, but only until the 4th-5th days. The antibiotic, chloram-phenicol, in doses of 10mg/fish/day, resulted in survival of homo-grafts until the 5th day. Tetracycline (1 mg) permitted survival of some grafts until the 7th day. Daily injections of 5 mg of 5 different serine and phenylalanine analogues slightly prolonged homograft sur-vival(to the 4th day), while ethionine, given in a dose of 3.3 mg/day, delayed the homograft reaction until the 5th day. These results indicate that antibody production depends upon nucleic acid synthesis, where it is most vulnerable to analogue interference. Inhibition of protein synthesis by adrenal cortical hormones or antibiotics is somewhat less effectual. Administration of amino acid analogues was least effective in preventing antibody synthesis.