Changes in adenine nucleotides of intact Chromatium D produced by illumination

The total adenine nucleotide content of suspensions of Chromatium D averaged 14 nmoles/mg of dry weight. Of this, one-third to one-half was adenosine triphosphate (ATP), even in suspensions incubated in darkness. Illumination with high intensities caused a rise in ATP and a drop mainly in adenosine diphosphate, the new steady state being reached in 5 to 15 sec at room temperature. The dark steady state was re-established 15 to 30 sec after returning the suspensions to darkness. The rates of these changes were little affected by the presence of electron donors or CO(2), though their magnitude was reduced when substrates were added to starved suspensions. At limiting light intensities, complex kinetics characterized the transition from both dark to light and light to dark, and, at lower light intensities, more ATP was produced in suspensions supplemented with electron donors than in starved cells. The results show that photophosphorylation accompanying cyclic electron flow occurred in intact cells, and suggest that noncyclic phosphorylation can also occur.

The comparative contraceptive activities of 10-beta-hydroperoxy-17-alpha-ethynyl-4-estren-17-beta-ol-3-one (SCH 10015) and norethynodrel

10β-Hydroperoxy-17α-ethynyl-4-estren-17β-ol-3-one (Sch 10015) was found to be less progestational than norethynodrel but equally potent as a contraceptive agent in rats. To prevent pregnancy in all the treated females, a minimum daily dose of 5 mg./kg. body weight (MPD 100) of either agent was required. At this dose, both agents had similar contraceptive mechanisms of action. They partially blocked the release of pituitary gonadotrophin and when given on the 2nd and 3rd day after coitus, i.e. after ovulation, prevented conception. Pituitary gonadotrophin inhibition is not considered to be the primary mechanism of contraception because significant numbers of rats ovulate when treated with the MPD 100 of either compound. It is concluded that the time of the primary contraceptive action of these agents at their respective MPD 100 is post-ovulatory.

It would appear from these experiments that classical progestational activity is not required for the contraceptive action of these drugs.