Hormonal measurement in rat anterior pituitary cell cultures: Loss of immunoreactive LH counteracted by fetal calf serum and bacitracin

Abstract

Immunoassayable LH in media samples from rat anterior pituitary cell cultures declines during storage and only 20% of the LH remains after 4 weeks at -20°C. The LH loss was not due to bacterial contamination or to damage to the hormone from repeated freezing and thawing. SDS-PAGE of 125IrLH in media samples showed greater recovery of 125IrLH when 1 mM bacitracin or 2% fetal calf serum were present in the medium. The ratio of intact: subunit 125IrLH was unchanged by the presence of bacitracin or fetal calf serum indicating that the loss of immunoreactive LH was not due to dissociation of intact hormone. LH appears to be irreversibly altered in stored culture media, a process which can be prevented by the addition of bacitracin or fetal calf serum to the media prior to storage. The use of either substance allows accurate and reproducible measurement of LH released from pituitary cells in culture.