A study was conducted to investigate the effect of differential dose levels of methylxanthines on lactational performance, with respect to milk volume and composition and pup growth. The methylxanthines; caffeine, theophylline and theobromine, were administered via drinking water in the proportions occurring in tea, at a dose of 50, 1 and 2 mg/kg body-weight respectively to Wistar albino rats throughout pregnancy and for up to the 14th day of lactation. A fourth group received a mixture of all three methylxanthines. Maternal food and fluid intake and weight changes, as well as weight gain in the litter were monitored thrice weekly. Milk samples were collected from the dams on days 7 and 14 of lactation, while milk volume was measured on days 12-13 by a method using tritiated water. Results showed that caffeine and theobromine significantly enhanced litter weight (P < 001 and 0.05 respectively). In the caffeine group, enhanced litter growth was due to a significant increase (P < 0.05) in milk volume, consequent to increased maternal food intake (P < 0.05). In the theobromine group there was only a weak association between increased litter weight and milk volume. Theophylline had no effect on the volume or composition of milk, or litter weight. The combination of all three methylxanthines also failed to produce any of the positive effects observed with separate drug treatments.

Caffeine, theophylline and theobromine are commonly consumed methylxanthines. There are conflicting reports that methylxanthines may adversely affect the outcome of pregnancy. The effects of methylxanthines on lactational performance were investigated by administration of pure alkaloids via drinking water to Wistar albino rats throughout pregnancy and lactation. Litter growth was used as an index of lactational performance in relation to maternal food and fluid intake, changes in weight, and lipid content of the carcass. Caffeine induced increased fluid intake (p < 0.01). While theophylline produced no significant differences in litter growth, maternal weight and carcass fat during pregnancy/lactation compared with controls, caffeine and theobromine significantly enhanced litter growth (p < 0.05 and 0.01, respectively). The enhancement in pup growth did not involve increases in maternal food intake or maternal lipid mobilization.

A novel, apparently acid‐stable cytochrome has been purified from Leptospirillum ferrooxidans in which it probably functions in the ‘downhill’ transfer of electrons from ferrous iron. It appeared to comprise a single polypeptide of apparent Mr 17.9 kDa as determined by SDS‐PAGE. Non‐denaturing PAGE showed this to be the approximate size of the native protein. The oxidized cytochrome showed a broad absorption maximum at 422 nm and was readily reduced with dithionite or ferrous iron to give a form with absorption maxima at 440 and 579 nm. A mid‐point potential of +680 mV at pH 3.5 was determined. Iron and zinc were found at concentrations approaching one atom of each per cytochrome molecule.