Role of lipoproteins and prolactin in luteal function in the ferret.

This study investigated luteal function in vitro during early pregnancy and pseudopregnancy in the ferret. Corpora lutea taken from animals on Day 13 following the ovulatory stimulus (mating or gonadotropin treatment) were dissociated with collagenase and incubated with ovine prolactin (Prl), ovine luteinizing hormone (LH), total lipoprotein fraction from canine serum, canine high-density lipoproteins (HDL), canine low-density lipoproteins (LDL) or combinations of Prl, LH, HDL, and LDL. Total lipoproteins produced statistically definable increases in progesterone accumulation in incubation media at 5 microliter (approx. 50 micrograms protein) through 25 microliter (250 micrograms protein) of the total lipoprotein solution. LDL in doses of 1 or more microgram protein stimulated progesterone accumulation in 2-h incubations and a similar stimulation was observed in the presence of 60 or more micrograms HDL. Prl, LH or the combination of Prl and LH had no apparent stimulatory influence on progesterone accumulation in vitro. Prl in combination with LDL further stimulated progesterone output by luteal cells in short-term incubation relative to LDL alone. Prl and LH together with LDL produced an increase in stimulation over LDL alone, but, for the most part, this augmentation did not exceed that recorded in the presence of the combination of Prl and LDL. No interactions between HDL and luteotropic hormones were present. The results indicate that lipoproteins increase progesterone output from ferret luteal cells, presumably by providing substrate for steroid hormone synthesis. No direct role for LH in ferret luteal function emerged from these experiments.(ABSTRACT TRUNCATED AT 250 WORDS)