Regulation of lactose production by ovine mammary acini in culture

T.B. McFadden, M.R. Callaghan, S.R. Davis

AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton, New Zealand

Proceedings of the New Zealand Society of Animal Production. 1995, 55: 17-20

Our objectives were to examine the effects of milk stasis, in vivo, and cell density, in vitro, on lactose production by cultured mammary acini from lactating ewes. In each of six lactating ewes, lambs were prevented from suckling one mammary gland to cause milk stasis in that gland. The opposite gland served as the control. Mammary acini were isolated and their lactose production during 24 h of incubation was measured.

Milk stasis markedly reduced lactose output (4.8 vs 2.5 fmol/cel/h;P<0.001). This effect was not altered by varying cell density or adding lactogenic hormones and foetal calf serum to culture medium. However, acini seeded at 2.5 x 10(5) cells/well produced nearly 5 times more lactose than those seeded at 2.5 x 10(6) cells/well(6.0 vs 1.3 FMOL/CELL/H; p<0.001). In further experiments, doubling the media volume from 1 to 2ml/well did not affect lactose output or relieve the density effect (P>0.10). In contrast, doubling the plating area significantly increased lactose output (P<0.05).

These data suggest that the milk stasis effect is exerted upon the mammary secretory cells because the effect was carried over into culture. The density effect appears to be mediated by cell to cell contact, rather than by nutrient limitation or diffusible inhibitors.

Keywords: NZSAPAB; Lactose; ovine; mammary; milk stasis; cell density; cell culture

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Last Updated 25-01-1997