The involvement of prostaglandins in eggshell formation in the domestic fowl was investigated by considering the effects of the drug indomethacin on the calcium metabolism on the eggshell gland. Egglaying birds were given a single dose (100 mg) of indomethacin at the beginning of shell calcification. Fourteen hours later the birds were sacrificed and the effects of the drug were determined. There was a 21% reduction in the shell thickness of the egg present in the shell gland at the time of slaughter (P < 0.01). The calcium content of the eggshell gland mucosa was increased to 153% (P < 0.01) of the controls. In the treated birds, there was 43% more calcium (P < 0.05) present in the shell gland lumen (recovered by rinsing with Tris buffer) than in the gland lumen of control birds. Total calcium in blood plasma was decreased by 15% (P < 0.05). In homogenate and three subcellular fractions (MIII, FI and FIII) of eggshell gland mucosa, 45Ca uptake was significantly reduced (i.e. by 29%, 25%, 17% and 35%, respectively). A significant reduction (62-66%) was also observed in the synthesis of PGF2 alpha, PGE2 and TxB2 by eggshell gland mucosa homogenate. 2. The effects of indomethacin treatment on the calcium metabolism of the avian eggshell gland are discussed and compared with p,p-DDE-induced alterations in calcium metabolism and prostaglandin synthesis by the eggshell gland.
