The glycoprotein hormone family represents a class of heterodimers, that includes the placental hormone equine chorionic gonadotropin (eCG) and the anterior pituitary hormones- follitropin (FSH), lutropin (LH), and thyrotropin (TSH). The 4 hormones are heterodimers, with a common $alpha$-subunit and unique $eta$-subunits. eCG is the most heavily glycosylated of the known pituitary and placental glycoprotein hormones. Recent observations using single chain glycoprotein hormone analogs in which, the $eta$-and $alpha$-subunits are linked, implied that heterodimeric-like quaternary configuration is not a prerequisite for receptor/signal transduction. To study the function and signal transduction of tethered rec-eCG, a single chain eCG molecule was constructed and rec-eCG protein was produced. Molecular mass of the single chain is about 45 kDa. All mice were ovulated by tethered rec-eCG treatment. The dual activity of tethered rec-eCG was determined in receptor cell lines of nonequid species; in fact, this dual activity was proven in species other than horse. Tethered rec-eCG in equids does not bind to FSH receptors, suggesting that eCG is primarily an LH-like hormone in the horse. Taken together, these data suggest that tethered rec-eCG has dual activity in nonequid species in vitro. However, it has only LH-like activity in equid species in vitro.