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To investigate the role of ryanodine receptors in glomerular arterioles, experiments were performed using an isolated perfused hydronephrotic kidney model. In the first series of studies, BAYK-8644 (300 nM), a calcium agonist, constricted afferent (19.6 [+ or -] 0.6 to 17.6 [+ or -] 0.5 [micro]m, n = 6, P < 0.01) but not efferent arterioles. Furthermore, BAYK-8644 elicited afferent arteriolar oscillatory movements. Subsequent administration of nifedipine (1 [micro]M) inhibited both afferent arteriolar oscillation and constriction by BAYK-8644 (to 19.4 [+ or -] 0.5 [micro]m). In the second group, although BAYK-8644 constricted afferent arterioles treated with 1 [micro]M of thapsigargin (19.7 [+ or -] 0.6 to 16.8 [+ or -] 0.6 [micro]m, n = 5, P < 0.05), it failed to induce rhythmic contraction. Removal of extracellular calcium with EGTA (2 mM) reversed BAYK-8644-induced afferent arteriolar constriction (to 20.0 [+ or -] 0.5 [micro]m). In the third series of investigations, ryanodine (10 [micro]M) but not 2-aminoethoxyphenyl borate (100 [micro]M) abolished afferent arteriolar vasomotion by BAYK-8644. In the fourth series of experiments, in the presence of caffeine (1 mM), the stronger activation of voltage-dependent calcium channels by higher potassium media resulted in greater afferent arteriolar constriction and faster oscillation. Our results indicate that L-type calcium channels are rich in preglomerular but not postglomerular microvessels. Furthermore, the present findings suggest that either prolonged calcium influx through voltage-dependent calcium channels (BAYK-8644) or sensitized ryanodine receptors (caffeine) is required to trigger periodic calcium release through ryanodine receptors in afferent arterioles. glomerular circulation; voltage-dependent calcium channel; caffeine; BAYK-8644; tubuloglomerular feedback

Abstract Background In practice, it is difficult to compare the effectiveness of traditional antihypertensive treatment with that of health promotion in reducing incidence rate of cardiovascular disease (IRCVD, events/year). This simulation study compared the effectiveness of two approaches to reducing IRCVD in a sample population: a traditional approach, in which high-risk patients are treated with conventional antihypertensive medications, and a population-based approach, in which subjects participate in a health promotion program. Methods We constructed a simulation model for a sample population of middle-aged Japanese men whose systolic blood pressure (SBP) levels are normally distributed (130 ± 20 mm Hg). The principal assumption was that IRCVD increases exponentially according to SBP. The population IRCVD was calculated as the product of the distribution of SBP multiplied by IRCVD at each SBP. The cumulative IRCVD was calculated by the definite integral from the lowest to the highest SBP of IRCVD at each SBP level. The success rates were calculated according to SBP and metabolic risk profiles in the two approaches, respectively. Results The reduction in IRCVD was twice as large for antihypertensive medications as it was for health promotion in several situations. For example, if adherence to antihypertensive treatment occurred at a realistic level, the decrease in IRCVD was estimated at 9.99 × 10-4. In contrast, even if the health program was promoted optimistically, the decrease in IRCVD was estimated at 4.69 × 10-4. Conclusions The success rate-oriented simulation suggests that prescribing antihypertensive medications is superior to promoting the health promotion program in reducing IRCVD in virtual middle-aged Japanese men.

Objective: This simulation study attempted to infer the systolic blood pressure (SBP) levels at which subjects with hypertension, health nurses, and primary physicians should switch their preference of their treatment policies from lifestyle modifications to antihypertensive medications in virtual Japanese sample populations. Methods: We assumed that SBP levels were normally distributed and that the incidence rate of cardiovascular disease (IRCVD, events/year) increased exponentially according to SBP. The total IRCVD was calculated by the definite integral for the product of the distribution of SBP multiplied by IRCVD at each SBP level. The success rates were calculated according to SBP and metabolic risk profiles in the two approaches, respectively. We deduced the hypothetical SBP levels by solving differential equations of ∆(IRCVD)/ ∆(SBP) = 0 using numerical analysis. Results: In the realistic situations where the subjects were not affirmative to antihypertensive medications, the inferred SBP level to switch from lifestyle modifications to antihypertensive medications should be around 150 mmHg. If the subjects are affirmative to antihypertensive medications, the SBP level should be lowered to 140 mm Hg. Conclusion: This success rate-oriented simulation proposes that the SBP level to switch from lifestyle modifications to antihypertensive medications can be modulated according to the behavioral propensity for taking antihypertensive medications. Abbreviations: The following abbreviations are used in this manuscript: CVD: cardiovascular disease; LM: lifestyle modifications; AM: antihypertensive medications; IRCVD: incidence rate of cardiovascular disease (events/year); SBP: systolic blood pressure; ∆IRCVD: the improvements in the incidence rate of cardiovascular disease by lifestyle modifications and/or by antihypertensive medications. [ABSTRACT FROM AUTHOR]

Epistasis used to be considered an obstacle in mapping quantitative trait loci (QTL) despite its significance. Numerous epistases have proved to be involved in quantitative genetics. We established a backcross model that demonstrates a major QTL for hypertension (Ht). Seventy-eight backcrossed rats (BC), derived from spontaneously hypertensive rats (SHR) and normotensive Fischer 344 rats, showed bimodal distribution of systolic blood pressure (BP) values and a phenotypic segregation ratio consistent with 1:1. In this backcross analysis, sarco(endo)plasmic reticulum [Ca.sup.2+]-dependent ATPase (Serca) II heterozygotes showed widespread bimodality in frequency distribution of BP values and obviously demonstrated Ht. First, in genome-wide screening, Mapmaker/QTL analysis mapped Ht at a locus between D1Mgh8 and D1Mit4 near Sa in all 78 BC. The peak logarithm of the odds (LOD) score reached 5.3. Second, Serca II heterozygous and homozygous BC were analyzed separately using Mapmaker/QTL. In the 35 Serca II heterozygous BC, the peak LOD score was 3.8 at the same locus whereas it did not reach statistical significance in the 43 Serca II homozygotes. Third, to map Ht efficiently, we selected 18 Serca II heterozygous BC with 9 highest and 9 lowest BP values. In these 18 BC, the peak LOD score reached 8.1. In 17 of the 18, D1Mgh8 genotypes (homo or hetero) qualitatively cosegregated with BP phenotypes (high or low) (P [is less than] 0.0001, by chi-square analysis). In conclusion, selective genotyping with epistasis can be utilized for a major QTL mapping near Sa on chromosome 1 in SHR.