Endotoxin of Escherichia coli and permeability of the mammary gland of goats.

Serial collections of milk were used to determine where in the mammary gland endotoxin of Escherichia coli was effective in altering the transfer of selected milk components into blood and blood components into milk. Lactating goats had half the gland infused with 1 microgram of endotoxin and the other half served as a control. Sodium-24 and 42K or [14C] lactose were included with 141Ce in the infusate in some experiments, whereas in others 99mTc-labelled albumin or 24Na and 42K were given intravenously 2 h after the endotoxin infusion. Milk was collected 3 h after endotoxin infusion. Endotoxin increased the loss of 24Na, 42K, and [14C] lactose from the mammary gland and increased the transfer of 24Na and 99mTc-albumin into the gland. The transfer in of 42K was reduced compared with control halves. Movement of stable Na and K was in accord with the movement of the 24Na and 42K. Endotoxin was effective in all parts of the gland but particularly from the mid-portion upward to the alveoli. For the control halves there was evidence that some 24Na and 42K crossed the ductal or cisternal epithelium into blood outside of the alveoli, whereas only 42K provided evidence for transfer from blood to milk in these same regions. There was no demonstrable transfer of lactose and albumin in regions other than the alveoli.

Effects of endotoxin on mammary secretion of lactating goats.

The objectives were to describe the magnitude and time course of changes in milk pH, Na, K, lactose, and somatic cells and to determine if paracellular pathways were altered after infusion of Escherichia coli endotoxin (serotype #0128:AB12) to produce inflammation in one-half of the udder of the goat. Intramammary infusion of endotoxin increased pH, number of somatic cells, and Na and decreased K and lactose in milk. Sodium and number of somatic cells were increased by as little as .1 microgram of endotoxin; .25 microgram produced changes in most of the other parameters; maximal effect was elicited by 1 microgram of endotoxin. The gland response peaked from 5 to 7 h after infusion of endotoxin with an increase in milk cellularity as the only significant effect noted in the control gland. Infusion of [14C]lactose into the gland and [99mTc]albumin into the blood demonstrated that large molecules were more able to cross into and out of udder halves after endotoxin treatment. It is suggested that ion interchange rather than bulk flow across paracellular paths is responsible for changes. In addition, endotoxin appeared to reduce lactose secretion and synthesis.