Comparative hospitalisation and mortality rates of aboriginal and non-aboriginal Western Australians in their sixth and seventh decades

BACKGROUND

Aboriginals have higher hospitalisation and mortality rates and die, on average, about 15 years earlier than non-Aboriginals in Western Australia (WA).

AIMS

To investigate Aboriginal morbidity and mortality rates in WA in comparison with the rest of the population, with particular reference to the ages of 50 to 65 years.

METHODS

Mortality rates from 1983-1989 inclusive for Aboriginals and non-Aboriginals in WA were compared. Major causes of Aboriginal mortality in males and females were matched to the ages at which similar rates from the same causes occurred in non-Aboriginals. Rate ratios (Aboriginal:non-Aboriginal) for causes of death at ages 60-64 years were determined. Hospitalisation rates for Aboriginal and non-Aboriginal people aged 50-64 years in WA in 1988 were used to estimate hospitalisation rate ratios.

RESULTS

Hospitalisation rates in WA were much higher among 50 to 64 year old Aboriginals than non-Aboriginals for most diseases, particularly for infectious and parasitic diseases, and injury and poisoning. Admissions for circulatory diseases were double to four times as frequent among Aboriginals. The main causes of deaths in Aboriginal males were circulatory diseases, injury and poisoning, respiratory diseases, neoplasms, and digestive diseases; in Aboriginal females the main causes of deaths were circulatory diseases, neoplasms, diabetes, respiratory diseases, and injury and poisoning. Except for neoplasms, deaths from these causes occurred among 50-54 year old Aboriginals at rates that were experienced by non-Aboriginal people ten to 30 years later in life. These results underline special needs of the Aboriginal population that have not been adequately met by appropriate services.

Patterns of mortality in Western Australian aboriginals, 1983-1989

The ratios of age-standardized mortality rates of Aboriginals to non-Aboriginals in Western Australia during the period 1983-1989 were 2.6 for males and 3.0 for females. Mortality rates experienced by Aboriginals were much higher in all age categories except 75+ years and for most major diseases except neoplasms. The peaks of all-cause age-specific mortality rate ratios (RR) for Aboriginal males and females were 10.2 (at 40-44 years) and 10.0 (at 35-39 years), respectively. These excess mortalities were mainly due to circulatory diseases, injury and poisoning, respiratory diseases and, in females, to digestive diseases and genitourinary diseases. The highest age-standardized, cause-specific RR for Aboriginal males were for mental disorders (10.3), injury and poisoning (8.9) and genitourinary diseases (8.6); for females the highest RR were for genitourinary diseases (16.9), endocrine, nutritional and metabolic (mainly diabetes mellitus) (12.3), and for infectious and parasitic diseases (7.5).

Circumvention of tamoxifen resistance by the pure anti-estrogen ICI 182,780

Both primary and acquired resistance to the growth-inhibitory effects of anti-estrogens (e.g., tamoxifen) limits the clinical usefulness of these drugs in the treatment of breast cancer. The new, steroidal anti-estrogen ICI 182,780 was tested for its ability to inhibit the proliferation of a tamoxifen-resistant variant of the parental MCF-7 human breast-cancer cell line. Two cell lines cloned from the MCF-7 line were used for these experiments: a tamoxifen-sensitive line, MCF 5-21, and a tamoxifen-resistant line, MCF 5-23. Compared with tamoxifen, ICI 182,780 appeared to be 150 and 1540 times more effective in inhibiting cell growth in the 5-21 and 5-23 sub-lines respectively. ICI 182,780 completely circumvented tamoxifen resistance at a concentration of (5 to 10) x 10(-9) M in this model. Based on IC50 concentrations, the 5-23 line was 22-fold more resistant to tamoxifen than the 5-21 line, but only 2-fold more resistant to ICI 182,780, reducing relative resistance by 10-fold in the resistant line. There were no differences in ER parameters between the 2 lines. ER numbers/cell were: 40500 and 34800 and the KD 0.48 and 0.15 x 10(-9) M in the 5-21 and 5-23 cells respectively. In the 5-23 cells, the concentrations of ICI 182,780 and tamoxifen resulting in a 50% inhibition of 3H-estradiol binding were 2.3 x 10(-8) M and 1 x 10(-6) M, respectively (cf. estradiol 0.89 x 10(-9) M). Thus, one potential mechanism for the increased effectiveness of ICI 182,780 may relate to the increased affinity of this drug for the estrogen receptor as compared with tamoxifen.

Effects of inhibitors of eicosanoid synthesis on insulin release by neonatal pancreatic islets

In the pancreatic islet, eicosanoids may arise from both cyclooxygenase- and lipoxygenase-dependent metabolism of arachidonic acid. The inclusion of inhibitors of selective steps in these pathways indicated that in cultured neonatal rat islets, arachidonic acid may be metabolised through both pathways, concurrent with insulin release stimulated by D-glucose, D-glyceraldehyde and 2-ketoisocaproate. The effects of the inhibitors suggested that the products of the lipoxygenase pathway were necessary for the stimulatory effects of nutrients to be observed. In contrast to glucose, where insulin release was stimulated in the presence of inhibitors of cyclooxygenase, the stimulatory action of D-glyceraldehyde, 2-ketoisocaproate and melittin was only minimally affected by these inhibitors, although it was inhibited by lipoxygenase inhibition. These findings support a major stimulatory role for products of the lipoxygenase pathway of arachidonic acid metabolism in nutrient-induced secretion, and a negative or modulatory role of cyclooxygenase pathway products on glucose-stimulated insulin release in the neonatal islet.

Captopril potentiates the vasodepressor action of Met-enkephalin in the anaesthetized rat

The transient vasodepressor action of Met-enkephalin (10-80 micrograms kg-1, i.v.) in anaesthetized rats was significantly potentiated by the angiotensin-converting enzyme inhibitor, captopril (2 mg kg-1, i.v.); at this dose, it failed to modify the transient vasodepressor action of the non-specific vasodilator, nitroprusside (2.5, 5.0, 10 micrograms kg-1, i.v.). Captopril (2 mg kg-1, i.v.) caused a slow, progressive fall in the blood pressure of anaesthetized spontaneously hypertensive (SH) rats when compared to vehicle-treated controls. Pretreatment with naloxone (1.5 mg kg-1, i.v.) 30 min earlier failed to alter significantly the hypotensive action of captopril in anaesthetized SH rats. It was concluded that although captopril potentiated the vasodepressor action of Met-enkephalin in anaesthetized normotensive rats, potentiation of endogenous opioids does not appear to be involved in the hypotensive action of captopril in anaesthetized SH rats.

Evidence for a functional central dopaminergic insufficiency in the spontaneously hypertensive rat

Several neuroendocrine abnormalities reported in the spontaneously hypertensive rat (SHR) suggest that the function of the dopaminergic tuberoinfundibular tract is impaired in this strain. SHR were pretreated with the peripheral acting inhibitor of dopa decarboxylase, carbidopa, or vehicle. Intravenous injection of L-dopa, the precursor of dopamine, lowered blood pressure only in the carbidopa treated SHR suggesting a central dopamine action. Intracerebroventricular injection of dopamine in SHR lowered blood pressure towards normal. The data are in agreement with the hypothesis that SHR have a functional central dopaminergic insufficiency.

Differences in arachidonic acid metabolism and effects of aspirin between one- and two-kidney Goldblatt hypertensive rats

Vasodepressor responses to prostacyclin, nitroprusside and arachidonic acid were compared in two groups of anaesthetized, two-kidney, one-clip Goldblatt rats. The groups were composed of rats which had high blood pressure (greater than 150 mmHg systolic) or normal blood pressure (less than 140 mmHg systolic). The vasodepressor effects of prostacyclin and nitroprusside and arachidonic acid did not differ significantly between hypertensive and normotensive groups when measured as percentages of resting blood pressure. Thus, in contrast to one-kidney Goldblatt hypertensive rats, there is no evidence for increased vascular conversion of arachidonic acid to prostacyclin in the two-kidney hypertensive model. The effect of cyclo-oxygenase inhibition on development of hypertension in one- and two-kidney Goldblatt rats was also studied by treating them daily with aspirin (200 mg/kg orally) from 3 days before until 3 weeks after clipping the renal artery. Aspirin-treated two-kidney rats developed significantly higher blood pressures than vehicle-treated controls, but the blood pressures of aspirin-treated one-kidney rats increased less after clipping than those of vehicle-treated controls. It appears paradoxical that transformation of arachidonic acid to prostacyclin is increased, while aspirin has a blood pressure lowering effect in one-kidney Goldblatt rats. It is suggested that there might be a more fundamental disturbance in arachidonate metabolism in hypertension which might contribute to increased vascular reactivity.

What stimulates the renin-angiotensin system in rats with two-kidney renal hypertension?

1. Blood pressure, the hypotensive effect of captopril, plasma renin activity, renal renin content and kidney weight were measured in the two-kidney—one-clip model, the one-kidney—one-clip model and the two-kidney—one-clip model with the ureter of the contralateral kidney ligated in rats. The ureteric ligation was performed to abolish urinary excretion from the contralateral kidney in the two-kidney—one-clip model.

2. The development of hypertension after renal artery constriction was earlier and greater in the one-kidney—one-clip model and the two-kidney—one-clip model with ureter of the contralateral kidney ligated than in the two-kidney—one-clip model. A single oral dose of captopril produced a greater fall in blood pressure in both the two-kidney models than in the one-kidney—one-clip group.

3. Plasma renin activity and renal renin content of the clipped kidney were higher in the two-kidney model rats, whether or not the ureter had been ligated, than in the one-kidney—one-clip model animals, although more than half the rats from the two-kidney model had normal values. There was a significant correlation between plasma renin activity and the response to captopril in all groups, whereas in none of the three groups was the correlation between plasma renin activity and blood pressure significant.

4. The clipped kidney had a higher renin content than did the contralateral kidney, and the weight of the ischaemic kidney was decreased compared with the contralateral kidney whether it was untouched or had its ureter ligated. The weight of the clipped kidney was in the order one-kidney—one-clip model > two-kidney—one-clip model with ureter of the contralateral kidney ligated > two-kidney—one-clip model.

5. It was concluded that the renin-angiotensin system was stimulated to the similar degree in some animals for the two-kidney—one-clip models, whether or not the ureter of the contralateral kidney had been ligated, compared with the one-kidney—one-clip animals. This finding suggests that the contralateral kidney can stimulate renin secretion and synthesis in the clipped kidney independently of Na+ excretion.

The effects of thyroid status on digoxin distribution in the rat

1. Tritiated digoxin was injected intravenously into euthyroid, hyperthyroid and hypothyroid rats. The rats were killed at intervals up to 24 h and tritium in serum and tissues counted. 2. Serum concentrations of tritium in the hyperthyroid animals were less than in the control group, whereas the concentrations in the hypothyroid group were similar to those in the control group. 3. Cardiac tissue concentrations of tritium were higher in the hyperthyroid group than in the control group, but in the hypothyroid group were similar to the control group. 4. The decreased serum levels in the hyperthyroid rats were probably due to an increased volume of distribution. 5. Pharmacological resistance to digoxin in hyperthyroidism must be due to some alteration in cardiac function and it is suggested that this is an increase in Na/K ATPase receptors.