Pregnancy protects against antiangiogenic and fibrogenic effects of angiotensin II in rat hearts.

AIM: To investigate the difference between physiological and pathological cardiac remodelling induced, respectively, by pregnancy and angiotensin (Ang) II, and to test the hypothesis that pregnancy protects against Ang II effects. METHODS: Female Wistar rats, pregnant (n = 12) and non-pregnant (n = 12), were implanted with mini-pumps containing saline (sham) or 150 ng kg(-1) min(-1) Ang II. Ten days later echocardiography and blood pressure measurement were performed. Expression of 22 genes was assessed using RT-PCR. Microscopic sections of LV were prepared to determine collagen content (Sirius Red staining), vessel density (ß-actin immunolabelling) and myocytes diameter (Toluidine Blue). RESULTS: Heart weight (HW) was increased in Ang II treated groups compared with their controls. Furthermore, HW of Ang II treated pregnant rats (1.0 ± 0.03 g) was higher than that in non-pregnant sham (0.7 ± 0.02 g), pregnant (0.8 ± 0.01 g) and Ang II treated non-pregnant (0.8 ± 0.02 g) rats. Relative LV wall thickness showed similar pattern. Aortic pressure was significantly increased in Ang II groups. Collagen content was increased in Ang II (4.0 ± 0.5%) compared with sham (1.5 ± 0.1%) but reduced again when treated rats were pregnant (2.8 ± 0.4%). Vessel density was reduced by 47.8% after Ang II treatment in non-pregnant and by only 13.9% in pregnant rats. Gene expression analysis showed increased expression of atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), anykrin repeat domain-containing protein 1 (Ankrd-1), protein kinase C-α and -δ and tumour suppressor gene TP53 (p53) in Ang II treated groups and upregulation of ANF, BNP and Ankrd-1 remained when pregnancy was combined with Ang II. Pregnancy reduced expression of: α-myosin heavy chain, tumour necrosis factor-α, p53, endothelial nitric oxide synthase and inducible nitric oxide synthase. CONCLUSION: Pregnancy seems to counteract the detrimental effects of Ang II on fibrosis and angiogenesis in heart. In addition, pregnancy and Ang II lead to partly opposite changes in the expression of some genes important for heart function.

Gene expression, function and ischemia tolerance in male and female rat hearts after sub-toxic levels of angiotensin II.

To examine the response to chronic high-dose angiotensin II (Ang II) and a proposed milder response in female hearts with respect to gene expression and ischemic injury. Female and male litter-matched rats were treated with 400 ng kg(-1) min(-1) Ang II for 14 days. Hearts were isolated, subjected to 30-min ischemia and 30-min reperfusion in combination with functional monitoring and thereafter harvested for gene expression, WB and histology. Ang II-treated hearts showed signs of non-hypertrophic remodeling and had significantly higher end diastolic pressure after reperfusion, but no significant gender difference was detected. Ang II increased expression of genes related to heart function (ANF, ß-MCH, Ankrd-1, PKC-α, PKC-δ TNF-α); fibrosis (Col I-α1, Col III-α1, Fn-1, Timp1) and apoptosis (P53, Casp-3) without changing heart weight but with 68% increase in collagen content. High (sub-toxic) dose of Ang II resulted in marked heart remodeling and diastolic dysfunction after ischemia without significant myocyte hypertrophy or ventricular chamber dilatation. Although there were some gender-dependent differences in gene expression, female gender did not protect against the overall response.

Glucose and fatty acid oxidation by the in situ dog heart during experimental cooling and rewarming.

BACKGROUND: Reduced myocardial function after hypothermia may be metabolic in origin, but the relationship between myocardial metabolism and the various components of hypothermia-mediated dysfunction has not been thoroughly investigated. METHODS: In the present study we measured myocardial uptake and oxidation of glucose and oleate in mongrel dogs undergoing cooling to 25 degrees C followed by rewarming to 37 degrees C, using radiolabeled substrates. RESULTS: Segment work index declined from 39.3 +/- 5.1 to 15.1 +/- 2.4 mm Hg in response to cooling from 37 degrees to 25 degrees C and did not recover completely on rewarming (27.2 +/- 4.2 mm Hg, p < 0.05). Oleate uptake declined from 3,251 +/- 619 to 1,043 +/- 356 nmol.min-1.100 g-1 (p < 0.05) when the dogs were cooled from 37 degrees to 25 degrees C. Simultaneously, oxidation rate fell from 1,089 +/- 158 to 354 +/- 83 nmol.min-1.100 g-1 (p < 0.05). On rewarming, oleate uptake was restored to prehypothermic values, whereas its rate of oxidation remained depressed (480 +/- 129 nmol.min-1.100 g-1; p < 0.05). Uptake and oxidation of glucose also declined significantly during cooling. However, both uptake and oxidation of glucose recovered fully on rewarming. CONCLUSIONS: The results of the present study demonstrate a reduced capacity to oxidize fatty acids by the myocardium during rewarming after hypothermia.

Lipid peroxidation, arachidonic acid and products of the lipoxygenase pathway in ischaemic preconditioning of rat heart.

OBJECTIVE: Preconditioning with brief intermittent periods of ischaemia is known to provide protection against ischaemic injury. It has been suggested that myocardial ischaemia also activates phospholipase A2, which releases arachidonic acid from phospholipids. In the present study the possible role of phospholipid peroxidation, arachidonic acid and products of the lipoxygenase pathway in cellular mechanisms of ischaemic preconditioning was examined. METHODS: Isolated, buffer-perfused rat hearts were freeze-clamped at the end of preconditioning (a cycle of 5 min global ischaemia +5 min reperfusion) and at the end of 30 min global ischaemia and analysed for non-esterified fatty acids and fatty acids in the 2-position of phospholipid. In a separate set of experiments, hearts pretreated with a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), were subjected to 30 min regional ischaemia and 120 min reperfusion. Infarct size was determined by tetrazolium staining and the ischaemic risk zone with fluorescent particles. RESULTS: Myocardial levels of arachidonic as well as of linoleic and docosahexaenoic acid were significantly elevated by preconditioning. Also, the level of peroxidized polyunsaturated fatty acids (measured as hydroxy conjugated dienes) in myocardial phospholipid was significantly increased: 101.4 +/- 16.8 nmol/g versus 51.2 +/- 7.3 nmol/g tissue dw in the control group, p < 0.05. Pre-treatment of hearts with 5 microM NDGA blocked the infarct limiting effects of preconditioning: infarct size was 37.4 +/- 6.4% of risk zone in control, 9.0 +/- 0.9% in the preconditioning group and 27.7 +/- 3.8% in the preconditioning + NDGA group (p < 0.05 vs. i.p., n.s. vs. control). CONCLUSION: Our findings provide evidence for the involvement of phospholipase A2 and lipoxygenase derived lipid second messengers in ischaemic preconditioning of the isolated rat heart.

Myocardial substrate oxidation during warm continuous blood cardioplegia.

BACKGROUND: Although long-chain fatty acids are a major energy substrate utilized by the myocardium, changes in the substrate balance toward a predominating fatty acid utilization could jeopardize the myocardium during cardiac operative procedures. METHODS: In the present study myocardial substrate utilization was examined during warm continuous blood cardioplegia (4 hours, 37 degrees C), using pigs undergoing cardiopulmonary bypass. Hearts were perfused antegradely in a closed extracorporeal circuit in which cardioplegic donor blood (hematocrit, 22%) containing 14C-glucose and 3H-oleate was delivered to the heart. Arterial and coronary sinus blood samples were taken at intervals for determination of plasma concentrations of energy substrates, as well as glucose and oleate oxidation rates (14CO2 and 3HOH production). RESULTS: The concentration of fatty acids in the cardioplegic perfusate did not change significantly during the cardiac arrest period. The mean concentration of glucose showed a 30% decline (not significant), whereas the lactate concentration increased from a starting value of 3.12 +/- 0.27 to 6.31 +/- 0.72 mmol/L at the end (mean +/- standard error of the mean; n = 8; p < 0.05). Only fatty acid levels showed a significant (positive) arterial-coronary sinus difference. Myocardial oxidation of oleate varied between 302 +/- 71 and 650 +/- 66 nmol.min-1.heart-1, whereas the range of variation for glucose oxidation was 144 +/- 64 to 355 +/- 107 nmol.min-1.heart-1. However, the changes in fatty acid levels and glucose oxidation rates during the cardiac arrest period were not statistically significant. We calculated that overall glucose oxidation accounted for less than 5% of the total aerobic energy production. CONCLUSIONS: The present results demonstrate overreliance on fatty acids as a source of energy during warm continuous blood cardioplegia, consistent with a condition of myocardial insulin resistance.