In vitro uptake of I131 by mammary tissue

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Abstract
In vitro uptake of I131 by lactating rat mammary tissue, incubated at 37°C for 6 hours, was 10–15 times that of liver, muscle or boiled mammary tissue. Uptake was greatly reduced by thiouracil and blocked by KSCN, NaCN or incubation under N2. It was increased to about twice the level observed in fresh mammary tissue after storage overnight at 7° C, but decreased rapidly during storage (with penicillin) at 37°C. I131 uptake by fresh mammary tissue was low during early pregnancy and increased sharply from 15 to 20 days of gestation. It increased further during lactation and decreased to minimal values after 10 days of mammary involution. Significant I131 uptake also occurred in lactating mammary tissue of mouse, guinea pig, rabbit and cow. Incubation of lactating rat mammary tissue with varying concentrations of prolactin, TSH, growth hormone, insulin or hydrocortisone had no effect on its I131 uptake. The data indicate that a simple enzyme system, not closely associated with respiratory metabolism, is involved in iodide collection by lactating mammary tissue. Though quite stable at 7°C, it is inactivated by boiling or by storage at 37°C.