Effects of prostaglandin on experimental bone malignancy and on scintigrams of bone and marrow

The correlation between prostaglandin E (PgE) and scintigrams of bone (Tc-99m MDP) and bone marrow (Tc-99m SC) was investigated in normal and VX-2-bearing rabbits. PgE in plasma of normal rabbits was 486.2 +/- 185.7 pg/ml (n = 86) and the maximum-to-minimum (max/min) ratio was 1.85 +/- 0.26 at 4 wk after tumor implantation. In rabbits with VX-2 transplanted into femoral muscles, PgE was in the normal range unless the tumor invaded bone. PgE did not increase significantly in rabbits when the tumor was transplanted into the marrow cavity. When tumor invaded bone, PgE increased markedly (to 1335 +/- 584 pg/ml). Elevation of PgE did not necessarily coincide with the appearance of positive bone scans. PgE in an indomethacin-treated group was not higher than in the untreated group. There was no significant difference between the two groups regarding the time of appearance of abnormal bone scans. However, when the number of transplanted cells in the bone marrow was reduced, the treatment with indomethacin delayed the increase in tracer uptake in the affected bone and resulted in a photon-deficient area. Indomethacin may suppress the local acceleration of calcium metabolism.