Recombinant Interferon-τ Regulates Secretion of Two Bovine Endometrial Proteins

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Abstract
Conceptus-derived interferon-τ (IFN-τ) has been implicated in the process of maternal recognition of pregnancy in the bovine. This type I IFN interacts with a uterine receptor complex to elicit secondary maternal responses, one of which is secretion of uterine proteins. We investigated the effects of pregnancy and recombinant (r) bovine (bo) IFN-τ (107 antiviral units/mg) on secreted proteins by cultured bovine endometrial explants. Explants were cultured for 24 h with [3H]leucine and dialyzed medium analyzed by one- and two-dimensional SDS polyacrylamide gel electrophoresis (PAGE) and fluorography. In one-dimensional PAGE experiments, endometrium representing early pregnancy (days 16–21) and the estrous cycle (days 16–19) was cultured in the presence of 5 nM rboIFN-τ and showed an increase (two- to five-fold) in secretion of 12- and 28-kD proteins. Further examination of these proteins by using two-dimensional PAGE indicated that the 12-kD protein was basic (pI ≥ 7.5), whereas the 28-kD protein was acidic (pI ∼ 5.0). Isoelectric focusing in the acidic range revealed that the 28-kD protein was composed of several isoelectric variants (pI 4.5–5.5). Although the functions of these secretory proteins are currently unknown, they serve as useful markers for IFN action and may act as secondary signals to protect the early developing conceptus.