Effect of post-mortem delay on density of tachykinin receptors in rat peripheral tissues

Abstract

The effect of post-mortem delay on the affinity and density of tachykinin NK 1 and NK 2 receptors was examined in the rat submandibular gland and gastric fundus, respectively, using saturation binding studies with the radioligands [ 125I]Bolton–Hunter [Sar 9, Met(O 2) 11]SP and [ 125I][Lys 5, Tyr(I 2) 7, MeLeu 9, Nle 10]NKA(4–10). For NK 1 receptors, no significant changes were seen in either K d (control 375 ± 35 pM, n = 5; 32 h post-mortem 390 ± 59 pM, n = 5) or B max (control 96 ± 16 fmol/mg protein, n = 5; 32 h post-mortem 62 ± 10 fmol/mg protein, n = 5). For NK 2 receptors, no alterations were seen up to 16 h post-mortem. However, significant ( p < 0.001) changes were seen at 32 h post-mortem ( n = 4), where values for K d were increased (3.0 ± 0.2 nM) and those for B max were reduced (42 ± 5.9 fmol/mg protein), relative to control ( K d = 1.3 ± 0.2 nM; B max = 208 ± 30 fmol/mg protein, n = 5). These changes are probably related to observed histological deterioration. This study demonstrates the stability of tachykinin receptors in these peripheral tissues and indicates the suitability of post-mortem tissue as a valid control in future tachykinin receptor studies.