No impact of polymorphism in the phosphodiesterase 5A gene in Cavalier King Charles Spaniels on pimobendan-induced inhibition of platelet aggregation response

Background: A variant in the canine phosphodiesterase (PDE) 5A gene (PDE5A: E90K) is associated with decreased concentrations of circulating cyclic guanosine monophosphate (cGMP) and response to PDE5 inhibitor treatment. Pimobendan is a PDE inhibitor recommended for medical treatment of certain stages of myxomatous mitral valve disease (MMVD) in dogs.Hypothesis: PDE5A:E90K polymorphism attenuates the inhibitory effect of pimobendan on in vitro platelet aggregation and increases basal platelet aggregation in Cavalier King Charles Spaniels (CKCS). Selected clinical variables (MMVD severity, sex, age, hematocrit, platelet count in platelet-rich plasma [PRP], and echocardiographic left ventricular fractional shortening [LV FS]) will not show an association with results.Animals: Fifty-two privately owned CKCS with no or preclinical MMVD.Methods: Using blood samples, we prospectively assessed PDE5A genotype using Sanger sequencing and adenosine diphosphate-induced platelet aggregation response (area under the curve [AUC], maximal aggregation [MaxA], and velocity [Vel]) with and without pimobendan using light transmission aggregometry. Dogs also underwent echocardiography.Results: Pimobendan inhibited platelet function as measured by AUC, MaxA, and Vel at a concentration of 10 mu M (P <.0001) and Vel at 0.03 mu M (P <.001). PDE5A:E90K polymorphism did not influence the inhibitory effect of pimobendan or basal platelet aggregation response.Conclusions and Clinical Importance: The PDE5A:E90K polymorphism did not influence in vitro basal platelet aggregation response or the inhibitory effect of pimobendan on platelet aggregation in CKCS. Dogs with the PDE5A:E90K polymorphism did not appear to have altered platelet function or response to pimobendan treatment

Polymorphisms in the serotonin transporter gene and circulating concentrations of neurotransmitters in Cavalier King Charles Spaniels with myxomatous mitral valve disease

Background The neurotransmitter serotonin (5-HT) affects valvular degeneration and dogs with myxomatous mitral valve disease (MMVD) exhibit alterations in 5-HT signaling. In Maltese dogs, 3 single nucleotide polymorphisms (SNPs) in the 5-HT transporter (SERT) gene are suggested to associate with MMVD. Hypothesis/Objectives Determine the association of SERT polymorphisms on MMVD severity and serum 5-HT concentration in Cavalier King Charles Spaniels (CKCS). Additionally, investigate the association between selected clinical and hematologic variables and serum 5-HT and assess the correlation between HPLC and ELISA measurements of serum 5-HT. Animals Seventy-one CKCS (42 females and 29 males; 7.8 [4.7;9.9] years (median [Q1;Q3])) in different MMVD stages. Methods This prospective study used TaqMan genotyping assays to assess SERT gene polymorphisms. Neurotransmitter concentrations were assessed by HPLC and ELISA. Results TaqMan analyses identified none of the selected SERT polymorphisms in any of the CKCS examined. Serum 5-HT was associated with platelet count (P < .001) but not MMVD severity, age or medical therapy and did not correlate with serum concentration of the 5-HT metabolite, 5-hydroxyindoleacetic acid. The ELISA serum 5-HT correlated with HPLC measurements (rho = .87; P < .0001) but was lower (mean difference = -22 ng/mL; P = .02) independent of serum 5-HT concentration (P = .2). Conclusions and Clinical Importance Selected SERT SNPs associated with MMVD in Maltese dogs were not found in CKCS and only platelet count influenced serum 5-HT concentration. These SNPs are unlikely to be associated with MMVD pathophysiology or serum 5-HT concentration in CKCS. HPLC and ELISA serum 5-HT demonstrated good correlation but ELISA systematically underestimated 5-HT