Sex differences in newborn myocardial metabolism and response to ischemia.

In children with congenital heart disease, female sex has been linked to greater in-hospital mortality associated with low cardiac output, yet the reasons for this are unclear. Therefore, we examined whether newborn sex differences in the heart's metabolic response to ischemia exist. Left ventricular (LV) in vivo and ischemic biopsies of newborn male and female piglets were compared.

Ventricle-specific metabolic differences in the newborn piglet myocardium in vivo and during arrested global ischemia.

Ventricular dysfunction is reported greater in the left (LV) versus right ventricle (RV) in infants following surgically induced ischemia. Ventricle-specific differences in baseline metabolism may alter response to ischemia thus affecting postischemic functional recovery. This study identifies ventricle-specific metabolic differences in the newborn (piglet) heart at baseline (working) and during ischemia (arrested).

Impact of female sex hormones on liver tissue lactic acidosis during ischemia.

Background: Lower liver transplant success is observed when the donor is female. Intracellular acidosis during ischemia is proposed to contribute to the injury sustained by the transplanted organ and its role in livers obtained from nonheartbeating donors is unclear. Research has shown that livers of female rats develop a greater degree of intracellular acidosis during ischemia than males.

Newborn hearts are at greater 'metabolic risk' during global ischemia--advantages of continuous coronary washout.

Background: Altered metabolic responses of the newborn heart to ischemia, which may increase irreversible injury, may at least partially explain the greater morbidity and mortality experienced by some children undergoing congenital cardiac repair. The present study compared newborn heart metabolic responses to global ischemia with those of adult, and evaluated whether continuous coronary artery washout in the newborn heart during 'ischemia' could favourably affect these responses.

Methods: Adult (n=12) and newborn (n=12) pigs were anesthetized, and right ventricular biopsies were taken before global ischemia and at set intervals during ischemia.

Are there ventricle-specific postnatal maturational differences in myocardial beta-adrenoceptors?

Newborn hearts have restricted functional reserve and variable responsiveness to inotropes that could be partly due to differences in myocardial beta-adrenoceptors (beta-AR). To clarify this issue, this study documented ventricle-specific changes in myocardial beta-AR density and affinity during postnatal maturation. In vivo left and right ventricle (LV and RV, respectively) biopsies were obtained from newborn (3-day-old, n = 11), immature (14-day-old, n = 7), and adult (n = 6) pigs.

Does hyperoxia affect glucose regulation and transport in the newborn?

Objective: Hyperglycemia has been found to occur in children placed on cardiopulmonary bypass. Our laboratory demonstrated that hyperoxia plays a role in this hyperglycemic response and also occurs in the absence of cardiopulmonary bypass. The purpose of this study was to elucidate potential mechanisms underlying the hyperoxic-induced hyperglycemia by examining glucagon, insulin, and epinephrine, which are important in glucose regulation and skeletal and cardiac glucose transporters (GLUT1 and GLUT4), which facilitate glucose entry.

Effect of hypertension on reproductive organ weights in various strains of rats.

The testes of Wistar Kyoto (WKY) and Spontaneously Hypertensive (SHR) rats have been shown to have differences in regional vascular resistance. In addition, myocardial hypertrophy tends to be more pronounced and occur more frequently in WKY and SHR female rats than in their male counterparts. Therefore, we sought to determine whether hypertension had any effect on reproductive organs and whether this effect was the same among strains.

Preischemic administration of ribose to delay the onset of irreversible ischemic injury and improve function: studies in normal and hypertrophied hearts.

Compared with normal hearts, those with pathology (hypertrophy) are less tolerant of metabolic stresses such as ischemia. Pharmacologic intervention administered prior to such stress could provide significant protection. This study determined, firstly, whether the pentose sugar ribose, previously shown to improve postischemic recovery of energy stores and function, protects against ischemia when administered as a pretreatment.

Body weight and food intake profiles are modulated by sex hormones and tamoxifen in chronically hypertensive rats.

Sex hormones and the selective estrogen receptor modulator tamoxifen affect food consumption and body weight in normotensive rats. This study investigated the effects of hormone manipulation and tamoxifen on weight gain and food intake in the presence of chronic systemic hypertension. Male and female spontaneously hypertensive rats (SHR) were either neutered or sham operated before puberty, and subgroups of neutered females received either estrogen replacement therapy (ERT) or tamoxifen at the age of 12 wk.

Special Feeding and Care of Senescent Spontaneously Hypertensive Rats.

This study investigated the impact of feeding methods on body weight of senescent female spontaneously hypertensive rats (SHRs) and showed that supplementing powdered feed was useful as they approached heart failure at 22 to 23 months of age. SHRs are genetically predisposed to systemic hypertension and will, with age, progress into complete heart failure resulting in death. Close to the time of heart failure, some rats experienced a loss of appetite and weight loss.

Multiple in vivo liver biopsies using a freeze-clamping technique.

A multiple in vivo liver biopsy technique was developed to measure labile metabolites (creative phosphate [CP], ATP, lactate) without interfering with normal perfusion and metabolism. Anesthetized rats (n = 7) had a midline abdominal incision done to expose the liver. Four biopsies were taken across 20 min.