Temporary disappearance ("eclipse") of LPC-1 plasmacytoma M component synthesis following tumor cell transfer.

The early phase of LPC-1 plasmacytoma development was studied by in vivo labeling with [6-14C]arginine using its M component (immunoglobulin G 2a,kappa) as marker. At a time when M component was not detected or faint by protein staining of electrophoretograms, significant labeling of M component was detectable by autoradiography. Labeling of the M component was fairly constant for the first 10 hr but was markedly decreased from Days 1 to 7. Nadir (0 to 3% of initial 30-min value) was observed on Day 3. Recovery of M component labeling to the 30-min level was complete by Day 13. This period of marked reduction or "eclipse" in newly synthesized M component was shortened by 2 days when mice were pretreated with pristane or cyclophosphamide prior to tumor cell transfer. The eclipse period was also 2 days shorter in athymic BALB/c-nu/nu mice than in normal BALB/c mice. The eclipse period corresponds to the classical "lag" following tumor cell transfer before tumor growth can be detected by conventional methods. The sensitivity of the [6-14C]arginine pulse permits the in vivo detection of small numbers of tumor cells (as few as 10(6) cells) over the early time periods after cell transfer. Modification of eclipse by manipulating host and/or tumor cells may elucidate the accompanying cellular and biochemical events.