A survey of some active sheep pineal fractions and a discussion on the possible significance of pteridines in those fractions in in vitro and in vivo assays

Lethal mutations induced in Drosophila melanogaster by direct or indirect action of pteridines

The experiments described in this paper show that synthetic pteridines, especially biopterin and pterin, injected directly into Drosophila melanogaster induce recessive lethals. On the contrary, D-neopterin seems to have little effect. A mutagenic effect has previously been shown for an extract of Pieris brassicae in diapause, treated with these pteridines and tetrahydrofolic acid (FH4). It appears that chromosome II is more sensitive to these mutagenic treatments than chromosome X.

Pteridines as nonretinal regulators of light-dependent melatonin biosynthesis

6-Formylpterin was purified by paper chromatography, and bovine pineal hydroxyindole-O-methyltransferase (S-adenosyl-L-methionine:N-acetylserotonin O-methyl-transferase; EC 2.1.1.4) was purified by flat-bed gel electrofocusing. Fractions of the methyltransferase with isoelectric points at pH 5.0, 5.7, and 5.2 were tested in the presence of 6-formylpterin, and decreased activities were found. Because 6-formylpterin is one of the photolytic products of folic acid and decreased serum folic acid has been reported in light-exposed men, we suggest that pteridines may be involved in nonretinal effects of light on pineal melatonin biosynthesis. It may be that this metabolic pathway is an evolutionary relic of primitive light responses of pigmentation mechanism.

Effects of sham-pinealectomy, performed under white and red light, on the melatonin content of rat pineal glands

Sham-pinealectomy, performed under different light conditons in newborn and adult rats, is followed by changes of pineal activity resulting in variations of melatonin content. The pineal glands of rats sham-operated under white light produce significantly less melatonin. In contrast, glands of rats operated on under red light show a melatonin content corresponding to that of intact rats. This result implies that normal white light causes a disturbance in melatonin production by a non-retinal pathway.