Abstract | OBJECTIVE: METHODS: Isolated working rat hearts were perfused aerobically for 10 min, and then subjected to 10-60 min of global ischemia. Control hearts were perfused aerobically for 30 min. [3H] PN 200-110 binding was measured in the unfractionated homogenate, in a crude membrane preparation and in a microsomal fraction. RESULTS: In the homogenate obtained from control hearts, the Kd and Bmax averaged 0.23 +/- 0.05 nM and 84 +/- 4 fmol/mg protein, respectively, and ischemia did not produce any significant change in these variables. Similar results were obtained in the crude membrane preparation (Kd = 0.29 +/- 0.08 nM, Bmax = 113 +/- 7 fmol/mg, yield of binding sites = 98 +/- 6%, no significant change in these variables during ischemia). On the contrary, in the microsomal fraction, the Bmax for [3H] PN 200-110 decreased after ischemia (115 +/- 15 fmol/mg after 20 min of ischemia vs. 190 +/- 34 fmol/mg in the control condition, P < 0.05), without any change in the Kd. In this fraction, the yield for PN 200-110 binding sites was 4.7 +/- 0.6% in the control condition and 2.8 +/- 0.5% after ischemia (P < 0.05). The yield of other sarcolemmal markers such as [3H]quinuclidinyl benzylate and [3H] ouabain binding sites was not reduced in the microsomal fraction obtained ischemic hearts. CONCLUSIONS: The total number of cardiac dihydropyridine binding sites was not downregulated during ischemia, although their distribution after tissue fractionation was slightly modified, possibly reflecting receptor redistribution between different subcellular pools.
|
Authors | R Zucchi, S Ronca-Testoni, G Yu, P Galbani, G Ronca, M Mariani |
Journal | Cardiovascular research
(Cardiovasc Res)
Vol. 30
Issue 5
Pg. 769-74
(Nov 1995)
ISSN: 0008-6363 [Print] England |
PMID | 8595625
(Publication Type: Journal Article)
|
Chemical References |
- Calcium Channels
- Calcium Channels, L-Type
- Receptors, Cholinergic
- Isradipine
|
Topics |
- Animals
- Calcium Channels
(metabolism)
- Calcium Channels, L-Type
- Cell Membrane
(metabolism)
- Down-Regulation
- Isradipine
(metabolism, pharmacology)
- Microsomes
(metabolism)
- Myocardial Ischemia
(metabolism)
- Myocardium
(metabolism)
- Perfusion
- Protein Binding
- Rats
- Rats, Sprague-Dawley
- Receptors, Cholinergic
(metabolism)
|