Abstract
Immunofluorescent staining was used to detect in situ alterations in inducible heat shock (stress) protein (HSP)-70 production and DNA fragmentation (indicative of apoptotic cell death) in luteal tissues obtained from sheep after in vivo administration of a luteolytic dose of PGF. Accumulation of HSP-70 was localized to PG-sensitive (i.e., large) luteal cells. Cytoplasmic HSP-70 increased within 2 h after treatment. Luteal concentrations of progesterone decreased precipitously thereafter. Expression of HSP-70 diminished by 16 h. An increase in immunostained digoxigenin-labeled DNA was not detected until the onset of structural involution at 16 h; both large and small steroidogenic cells were affected. It is suggested that HSP-70 induction by PGF is a prelude to steroid depletion and active apoptotic death of luteal cells.

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