Superfusion of Rat Anterior Pituitary Cells Attached to Cytodex Beads: Validation of a Technique*

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Abstract
A superfusion method consisting of fully recovered, dissociated pituitary cells adhering to Cytodex beads has proved useful in monitoring the dynamics of hormone secretion ver time. Male rat anterior pituitaries were dissociated with collagenase and Viokase, then cultured in the presence of Cytodex beads for 3–5 days, during which time the cells attached firmly to the surface of the beads. The bead-attached cells were stable and could be transferred to any vessel. without the need for centrifugation or further trypsinization. For this application, the bead-attached cells were packed in a column and superfused with a low bicarbonate buffer requiring no CO2 gassing. Viability was more than 95% after 48 h in the column. The cells responded in a normal physiological manner to hypothalamic releasing and inhibitory peptides. The ED50 was 0.3 nM for somatostatin and 1.2 nM for gonadotropin-releasing hormone. A postinhibitory rebound of GH secretion was observed after the discontinuation of large doses of somatostatin. LH secretion reached maximal levels within 6 min after 10 nM gonadotropin-releasing hormone, but started declining after 2 h of continuous stimulation and dropped close to baseline within 18 h. GH release was significantly increased by prostaglandin E2, 3-isobutyl-l-methylxanthine, and 8-bromo-cAMP. LH secretion increased 5-fold in response to 1 mM 8-bromo-cAMP, but showed little increase during prostaglandin E2 or 3-isobutyl-l-methylxanthine stimulation. The cocarcinogen phorbol myristate acetate (12-O-tetradecanoyl-phorbol-13-acetate) induced secretion of all pituitary hormones and continued to do so for hours after short pulse. The superfusion system is simple to operate and has proven effective in studying transient phenomena, desensitization, and short term kinetics of secretagogues.