Tissue levels of prostaglandin E following heterotopic rat heart allografting.

Heterotopic rat heart allografts were performed in 35 rats. At intervals after transplantation, rats were killed and tissue concentrations of immunoassayable prostaglandin E (PGE) were measured in the native heart, transplanted heart, spleen, and thymus. A significant increase in allograft PGE activity was observed at days 5 through 7, coinciding with the onset of the rejection reaction. These studies implicate PGE in the host response to allografting, but further studies are needed to determine what (if any) role prostaglandins play in the rejection reaction.

Alterations in kinins of coronary blood from rat heart homografts.

Forty-eight heterotopic heart transplants (33 homografts and 15 isografts) were performed in inbred rats. Levels of kallikrein, prekallikrein, and kallikrein inhibitor were determined in coronary sinus venous blood of grafted hearts at various intervals postgrafting. Homograft observations were assessed against those in nonrejecting isografts. Significant increases in homograft prekallikrein level on day 4 were followed by significant increases in homograft kallikrein activity on day 6. Kallikrein inhibitor levels in homografts were consistently increased in relation to isograft levels. Kallikrein and inhibitor activity showed an inverse relationship in their respective changes. High levels of kallikrein and prekallikrein occurred in homografts ten days posttransplantation. Immunological rejecting homografts showed meaningful changes in the activity of kinin-forming substances known to participate in inflammation.

Accumulation of 131I hippurate in rat heart allografts during rejection.

The accumulation of 131I hippurate in heterotopic (abdominal) rat heart allografts (Brown-Norway to Lewis) in comparison with native (autologous) hearts 6 and 7 days after transplantation was studied by noninvasive scintigraphic imaging and by direct isotope counting of excised hearts. Six hours after intravenous isotope injection, isotope accumulation in the allografted heart was clearly identified by scintigraphic study in comparison with the background, kidneys, urinary bladder, and native heart. Six and 7 days after transplantation, excised allografted hearts were significantly increased in weight in comparison with native hearts. A significant increase in isotope accumulation in allografted hearts in comparison with native hearts was found both per heart and per gram of heart. The findings of this study suggests the potential usefulness of 131I hippurate in the immunoinflammatory monitoring of organ allograft rejection by direct counting as well as by noninvasive scintigraphic study if sufficient time is allowed to permit clearance of high concentrations of isotope from the background areas, kidneys, and urinary bladder.