1) suppression of LH and free alpha-subunit secretion by P can be accounted for at least partly by suppression of alpha-subunit mRNA levels; 2) P facilitation is not associated with changes in LH subunit or GnRH mRNA levels; 3) the large proportion of cFos-positive GnRH neurons in P-facilitated rats closely parallels increases in serum LH concentrations but is not accompanied by changes in GnRH mRNA levels. It is likely, therefore, that P acts in the facilitation model to trigger release of pre-existing GnRH stores by altering synthesis or activity of neuro-transmitters/neuropeptides involved in GnRH regulation and/or release of LH stores by altering, for example, pituitary responsiveness to GnRH (including self-priming) and components of the LH secretory apparatus. Similar possibilities may also obtain for the blockade of the gonadotropin surge in the inhibition model.

Changes in the uterus of the mouse during the oestrous cycle and early development from 90 to 190 hr post coitum were examined to demonstrate variations in the occurrence of alkaline phosphatase (ALP) activity.

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SUMMARY The distribution and source of protein in the fluid compartments of tissues may be determined by the use of [14C]sucrose to determine the volume of the fluid compartments and 125I-labelled serum albumin ([125I]SA) to determine the distribution volume of the labelled protein. The amount of tissue protein in the ovary, the amount of protein derived from plasma, the rate of plasma protein influx into the ovary and the amount of newly synthesized protein were calculated. Immature female rats were treated with pregnant mare serum gonadotrophin (PMS)when 24 days old and were given human chorionic gonadotrophin (HCG) 42 h later. The rats were given [14C]sucrose or [125I]SA and measurements were made. Ovaries and blood were collected 0, 3, 5, 8 and 10 h after HCG administration. At all intervals the dry weight represented 14% and water 86% of the weight of the ovary. The extracellular space increased until 8 h and then both it and the intracellular space increased. At 0 h plasma protein accounted for 17% of the total proteins. At 10 h the ovarian weight had increased by 50% to 100% of the value at 0 h and the total protein by 45% of the value at 0 h with plasma protein accounting for 27% of the total proteins, and newly synthesized protein for 16%. The increase in plasma protein was linear and accumulated at the rate of 15%/h. By this method no entrance of plasma protein into the intracellular space could be demonstrated. Newly synthesized protein appeared only after 5 h and probably represents the growth of a new crop of follicles.