Ultrastructural changes in lactating guinea pig mammary gland slices associated with theophylline inhibition of lactose synthesis
Loizzi, R.F.; Amato, P.A.
Cytobios 22(85): 47-65
1978
ISSN/ISBN: 0011-4529 PMID: 753594 Document Number: 136408
Mammary gland slices from lactating guinea pigs were incubated for periods up to 1 h in 10-2 M theophylline, which completely inhibited lactose synthesis. Ultrastructural comparison with control slices showed a significant increase in the size of the Golgi field involving an apparent back-up of microvesicles. Normally distended Golgi cisternae were flattened and contained fewer, less dense protein granules. Theophylline decreased by 50% both types of secretory vacuoles present: a compact, 300 nm diam. vacuole containing one 250 nm granule, and a swollen, approximately 700 nm diam. vacuole with one or more granules. Changes in granule shape, density and formation were also observed. Results suggest that the site where theophylline inhibits lactose synthesis may be in the translocation of substances from the rough endoplasmic reticulum to the Golgi complex, possibly the specifier protein alpha -lactalbumin which is essential to the lactose synthetase complex. The significance to the role of cyclic nucleotides in lactation is discussed.