1. The distribution and multiple forms of
hexokinase activity in lactating rat mammary gland were investigated in
alloxan-diabetic rats and in rats treated with anti-
insulin serum. It was found that 46% of the total
hexokinase of mammary-gland tissue from control rats was in the particulate fraction, but this percentage was decreased in the
alloxan-diabetic rats to 11% of the total
hexokinase. The
hexokinase activity of the soluble fraction was not significantly altered but there was a decrease in the type II/type I quotient. 2. The early changes that occurred on
insulin deprivation were studied 1hr. after administration of anti-
insulin serum to lactating rats, at which time the
hexokinase bound to the particulate fraction had decreased to 11% of the control value and that in the soluble fraction had increased by approx. 50%. The
hexokinase type II/type I quotient in the soluble fraction was significantly decreased. These results suggested that there was a release of particulate-bound
hexokinase in rats treated with anti-
insulin serum.